LADY LAKE, Fla. – It’s 11 p.m. at the Bourbon Street Bar, and Roselyn’s gyrating her hips to the blues band, Sue’s sipping a cocktail and flirting with her new boyfriend, and Alan is scanning the crowd for cute girls.

“See those two?” a buxom blonde asks, pointing to an elegant couple at the bar. “They were caught having sex in their golf cart a few weeks ago. It happens a lot!”

Welcome to ground zero for geriatrics who are seriously getting it on.

It’s a Thursday night at one of a half-dozen hot spots at the 20,000-acre Central Florida complex called The Villages, the largest gated retirement community in America – and one of the most popular destinations for New Yorkers in their golden years – where the female-to-male ratio runs 10 to 1.

It’s a widower’s paradise, and the word on the street is that there’s a big black market for Viagra.

Though The Villages – which spans three counties with 40,000 homes and more than 70,000 residents – boasts 34 golf courses, nine country clubs, two downtown squares and a slew of restaurants and bars, getting lucky is one of the residents’ primary pastimes.

The huge complex began growing rapidly in the mid-1990s, and reported cases of gonorrhea rocketed from 152 to 245, of syphilis rose from 17 to 33, and of chlamydia from 52 to 115 among those 55 and older in Florida from 1995 to 2005.

The state’s sexually transmitted disease rate among those over 65 is one of the fastest growing in the country, one report claims.

In 2006, a local gynecologist reported that she treated more cases of herpes and human papillomavirus at The Villages than she did when she worked in Miami.

“I get offers for sex all the time,” brags Dave, 70, who, like others who spoke about their sexually active set, asked that his real name not be used, “especially by women in their 70s. They say, ‘Are you busy tonight? I’ll show you a good time.’ ”

One overly charming lady-killer known as “Mr. Midnight” boasted of one of his conquests last year: “Absolutely beautiful. I’ve had her a few times. She comes over, takes a shower, jumps in bed, and then gets dressed and leaves. She’s simply the best.”

His story was told by Andrew Blechman, author of “Leisureville,” about communities like The Villages.

“There is lots of romance around here,” said Jean, a 63-year-old retired teacher. “But most of the men want a one-night meaningful relationship.”

Her friend Louise agrees.

“A lot of the men down here are cheaper than heck,” she says, “and a lot of the women are extremely brazen. Some girls will go into the parking lot with a man and come back a half-hour later like nothing happened!”

“We’ve had some of those complaints,” said a laughing Lt. Laurie Davis of the Lady Lake Police Department, ticking off other offenses, like drunken driving in golf carts, illegal drug use, and bar fights.

“Whatever you know about 20-year-olds, it’s the same with seniors,” said Roselyn Shelley, 68, a divorced former dancer.

Sue Rice, a blonde who will only admit to being over 60 but who looks to be about 80 and dances like she’s 14, has hooked up with Larry Tucker, an ex-banker about a decade her junior.

Tucker sports a gold charm around his neck that reads, “Bankers do it with interest.”

“Feel this,” Rice says, bouncing up from her bar stool and pinching her slim waist. “My body is the same as it was in high school! He can’t keep up with me!”

According to Alan, a swarthy 62-year-old, there’s a thriving black market for little blue Viagra pills.

“I did it once,” he said. “I paid 12 bucks for a single pill.”

Local cops just try to keep up.

“You see two 70-year-olds with canes fighting over a woman and you think, ‘Oh, jeez,’ ” Lt. Davis said.

*Some names have been changed.

stefanie.cohen@nypost.com