Four weeks ago, just after 10 o'clock on a Saturday night in downtown Buffalo, New York, Orlando Cruz looked wistfully out the window as our car sped through the deserted streets. After a brutal day in the gym, sparring 12 rounds against four different opponents, he yearned for a fleeting escape from preparations for his first world title fight.

"There are only four gay bars in Buffalo," Cruz said, switching from Spanish to English, "and they're not so exciting. But ... you know ..."

Cruz laughed because, a year after coming out as boxing's first publicly gay fighter, he could afford to be open. He was a month away from the fight of his life, which takes place on Saturday night in Las Vegas as he challenges Mexico's Orlando Salido for the WBO world featherweight title, but he still loved his new liberty.

The temptation of slipping into a bar was obvious after months of monastic training. But boxing is merciless towards laxity and indulgence. Cruz's trainer, Juan de León, a fellow Puerto Rican, was also waiting for us at home in the suburbs of a blue-collar city deep in New York State. So we raced on through the darkness.

It was the night, last month, when Floyd "Money" Mayweather earned around $70m for outclassing the previously unbeaten hope of Mexico, Saúl "Canelo" Alvarez, in boxing's fight of the year. Mayweather, on pay-per-view television, offered a taster of everything that awaits Cruz.

"It's been my dream all my life," Cruz murmured as he considered his own world title fight. He sounded like a typical fighter then; and he also looked like one as the streetlights cast an eerie glow across his battered and suddenly pensive face. The idea of a gay boxer, which he introduced so calmly last October, has been accepted. Yet his dreamier notion – of becoming the world's first gay world champion – would bring Cruz the money and respect he has long craved.

Cruz, or Orlandito, as De León calls his 32-year-old fighter, smiled when I disappeared into the trainer's kitchen soon after we arrived. It felt rude not to accept De León's offer of a shot of tequila and cognac to get us in a big fight-night mood. Cruz remained in the sitting room, drinking water while we knocked back the hard stuff. But there was no stopping him when, after 1am, Cruz belted out the Mexican national anthem alongside the crooner singing it for Alvarez in Vegas. Cruz was as word-perfect when, the cameras trained on Mayweather, he hollered through the Stars & Stripes. He seemed to be having more fun here than in a Buffalo bar.

There was a cruel beauty to Mayweather's work as he speared blurring combinations into Alvarez. The raucous anticipation in De León's living room quietened as the Puerto Rican boxing men showed appreciation of a master of their vicious trade. Cruz was the most concentrated of all as he studied Mayweather.

Orlando Cruz, far right, gathers with friends at his trainer Juan De Leon's house to watch the Mayweather-Alvarez fight. Photograph: Herminio Rodriguez

At 2.15am, in the cool air outside following Mayweather's decisive win, Cruz stretched out his hand. "Four weeks tonight ... it's my turn."

That raw immediacy fills every sparring session at the Northwest Buffalo Community Centre because Cruz knows how hard he will have to fight. Salido has boxed professionally for 17 years – since he was 15 – and has won the IBF and WBO world featherweight titles. He is the same age as Cruz but has had 53 fights – 30 more than the Puerto Rican whose record of 20 wins, a draw and two defeats was shadowed by a fraught battle over his sexuality.

It took years for Cruz to find the courage to make history as a gay fighter. But now, released from the shackles of secrecy and guilt, he works with new intent. "He's had his time," he murmurs in Spanish of Salido. "Now it's my time. People think I'm not strong enough. They doubt me. They wonder if a gay man can win a world title."

Cruz shrugs bleakly and, for such a warm man, looks briefly angry. "The sceptics will see what I am capable of on 12 October."

He's still brooding over De León's rough treatment of him, and it's not long since he swore vehemently at his trainer. Cruz peels the bandages from his hands. They're soaked after two hours of training. He sinks into a chair, the mess of boxing shoes and bags strewn around him, resembling a gritty old fighter rather than a gay icon.

Sweat runs down his sunken face like tears. Last October, during his first newspaper interview as a gay fighter, Cruz told me how he used to cry with his mother, Dominga. She accepted his sexuality but he still hid the seemingly unspeakable truth about himself in public. He even cackled at the melodramatic picture they made, at her kitchen table, as he sobbed about not being able to come out in two worlds, Puerto Rico and boxing, built on machismo. But now, as the Salido bout hurtles towards him, his mind is less cluttered.

"I'm so focused on winning it doesn't matter how many fights Salido has had," he says. "This will be a new psychological challenge for him."

Cruz understands how this fight will smudge the boundaries between the personal and professional. He even implies that Salido, as a Mexican, might be troubled by facing a gay fighter. "My coming out made it harder for him. He will have it in his mind that he's fighting a homosexual for the world title."

Is he suggesting Salido might be homophobic? "He's professional with me but Mexicans often have something homophobic in them. It's the machismo culture. He won't want to lose to a gay man. Salido will be much more aggressive. He will want to make a statement because I'm gay. But he'll fall into the trap by being macho. I'll let him come at me, and I'll show him then. The only language I will use is spoken by my fists. They will do my talking."

Orlando Cruz rests during a sparks session at Buffalo Northwest Community Center boxing gym. Photograph: Herminio Rodriguez

Cruz is even more motivated by the memory of Emile Griffith – a six-times world champion who died this summer. Griffith fought more world championship rounds than any other fighter, even Sugar Ray Robinson and Muhammad Ali, and he was gay. In 2005 he finally admitted in public that he was, at least, bisexual. He also still felt a haunting pain over the death of Benny Paret, the Cuban fighter whose life had been extinguished beneath his fists after their world title fight in 1962.

Griffith was a generous and cheerful man, who often said that he would have been as happy being a flamboyant milliner making ladies' hats, but he reacted with cold ferocity after Paret taunted him as a maricón [faggot] before their tragic third fight. In the ring he pinned Paret against the ropes and, as if ripping the wings off a butterfly skewered to a board, landed 26 unanswered blows which stole the life from his once mocking opponent.

I visited Griffith in Long Island last December for he was one of my favourite boxers, ever since he and his trainer, Gil Clancy, arrived in the South Africa of my childhood, in 1975. Griffith was black, Clancy was white and apartheid ruled that they could not work together at a Soweto bout. But they refused to buckle and the government surrendered. It was an early introduction, for me, to the courage and decency of some boxing men.

Our plan had been that I would take Cruz to meet Griffith – even if severe dementia had ruined the former champion – so there would be a poignant encounter between boxing's only openly gay fighters. But we didn't make it. Griffith slid away, mercifully, in June.

Saturday night, in Vegas, will mark a more sombre memento from Cruz to Griffith. "I'm fighting for my family, my trainer, my team, everyone who wrote to me around the world since I came out, as well as the lesbian-gay-bi-transgender community," Cruz says. "They all brought grains of sand to the dream I've built. But I want to dedicate this fight to Emile Griffith. He had to live with the stigma of being black when there was such prejudice. And he was gay. He suffered from double prejudice – and the second was even worse because he kept it secret so long. He was a brave man, and a great champion, and so I want to win the world title for Emile."

De León joins us, in a stark dining hall next to the gym, and Cruz rolls his eyes at me as he listens to his trainer. "I love this kid," De León says, "but I was hard on him today. You've heard how important this fight is to Orlandito. Last October he released something he was holding inside him for so long. He's free now."

The trainer remembers Cruz beating up another fighter who had taunted him a few years ago for being gay. "Orlando had already confessed to me," De León says. "I had no problem. A couple of my cousins are gay or lesbian. I accepted him and we kept it secret. But this guy in the gym knew the rumours. When he and Orlando sparred he was kidding around. Orlando said: 'Keep your hands up because I'm hitting you.' But this fighter kept taunting him. He said: 'Hey, do what you gotta do, you fucking gay ...'"

De León glances at Cruz who says: "He called me maricón."

"Oh, Orlandito," De León sighs, "you opened up on him." He pumps his fists and cries: "Ba-ba-ba-bam, ba-ba-ba-bam! Orlando got him in the corner and said: 'I'm gonna fuck you up ...' Bam-bam-bam! You talking about me? How does it feel? A fucking gay beating you up?"

De León's eyes widen at the memory. "You know what it reminded me of? Griffith against Paret. That's how angry he was."

The truth, even when it's smeared with hurt and violence, matters to Cruz: "I was different then. I had a lot of pain in me. I carried a persecution complex."

De León confirms that, "back then Orlando didn't get on with my fighters. He thought they were all laughing at him because there was so much gossip. He would say to them: 'What you looking at?' I would say: 'Hey, Orlandito, people can look at you.' So that's why, when the guy called him maricón, Orlando cut loose. But guess what? They became good friends. The next day they both apologised and started working together. That's Orlando's strength."

A defining measure of that strength was established exactly a year ago when Cruz came out. It is striking that, now, he can concentrate more on his career than repeat why, as he told me last October, he removed "the thorn from my side".

"I'm much more tranquil now. My mind is on the fight. It was the same with my two other fights after coming out. I was calm and won easily. I'd said what I wanted to say for so long. I'm a gay man – and a fighter. This gives me calm."

Cruz felt more jittery when, three months ago, he proposed to his partner, José Manuel, on Facebook. "I'd like to say, and share it with your friends, and my friends: 'Do you want to marry me?' It's an important step, a step I've thought about, a step we've thought about ..."

It did not take long for José, who is older than Cruz and an engineer, to accept and tell Cruz: "I love and adore you."

Cruz looks almost dazed as he remembers his unusual proposal. "I came in after a long run and just did it. It was very spontaneous. Life is much more positive for me now. I have my boyfriend. I have so much support. I'm much more confident. My marriage can happen in a year or two but a world title fight against Salido is a once-in-a-lifetime chance."

Marriage between gay men is banned in Puerto Rico, as in many states of America, and so their struggle is not over. Cruz also recalls the homophobic murder of a close friend, a transvestite, in San Juan. "It happened two years ago and I will think of all the people who died in these hate crimes. But winning the fight will be the strongest message I can give."

We leave the gym and cross the street for lunch at the house belonging to De León's brother. Over steaming bowls of soup, Cruz plays with De León's baby niece, throwing her gently into the air as she squeals excitedly. "I would love to have kids," he says simply.

He and José will have to marry in New York and try to adopt children away from Puerto Rico where, again, the notion of gay parents is illegal. But, lost in the moment, Cruz echoes the little girl's laughter as he turns her into a small aeroplane and flies her around the kitchen. His battle with Salido seems an age away.

On my last day in Buffalo, Cruz suggests we go to church. He arrives late, having slept in, but he grins. "It's better I go to church than a gay bar," he says as we walk into St Joseph's where De León's 11-year-old son, Angel, is an altar boy. I find it hard to shake stark thoughts of everything Cruz will face against Salido – especially when his head is bowed in silent prayer. The hymns roll on – and Cruz sings quietly that Lord, I'm Coming Home. When we are asked to link hands he holds mine tightly while the priest prays for those about to face danger, or darkness.

Encouraged to turn to each other and say, "Peace be with you ...," Cruz shakes my hand and says the words sincerely. But he is a fighter and so he also winks.

Orlando Cruz prays during Catholic mass at St Josesph University Church in Buffalo, New York. Photograph: Herminio Rodriguez

Now, a month later in Las Vegas, the tension is palpable. At Thursday's final press conference for HBO's pay-per-view event the veteran promoter Bob Arum held court. He recalled his promotion of Muhammad Ali and hailed Cruz as another boxing pioneer who will wear pink gloves and multi-coloured trunks that look more like a skirt in the ring. Arum suggested that, even recently, a fight featuring a gay boxer would have led to the appearance of "a thousand protesters. But boxing, and the world, is a much better place now".

On the podium and wearing a smart charcoal-grey suit, Cruz smiled and spoke clearly in English. "Today I'm making history ... and on Saturday I'll be the new world champion." Salido cut a contrasting figure in a black tracksuit. The old Mexican warrior's usually stony face kept twitching. But he did not sound frightened when he said: "It's going to be a war."

Away from the hoopla, a quiet force runs through Cruz. He knows that, whatever happens, he will make history as the first publicly gay fighter to challenge for a world title.

"Everything I've been through has taken me to this point," Cruz says in one last moment of private reflection before we part. "It's the most important fight of my life. I'm a gay man, but I'm also a boxer. My two worlds have come together and I will fight with all my heart. The world knows the truth about me as a man. Now the world will see the truth about me as a fighter. I'm ready. This is my time."