On a dusty highway in California's Central Valley, a black Chevy truck heads toward bright fields of grapes dotting the barren brown earth. It is a warm June day, and the truck's windows are cracked open to get a little air. Out wafts a rap song: Spanish rhymes interspersed with the occasional English phrase —"hell yes." Toward the middle of the song a third language beats its way in.

"That is Mixteco," says the driver, Miguel Villegas.

Mixteco is Villegas's native language. It is the only language he spoke fluently when he came to the United States sixteen years ago at the age of seven. The trilingual rap song is his own creation and he takes to heart its Spanish language refrain: "Mixteco is a language, not a dialect. It's the gold that I treasure."

Villegas spent two years working in the grape fields where his older siblings still toil. Now he is a community worker at the Fresno headquarters of the Binational Center for the Development of Oaxacan Indigenous Communities, a nonprofit that focuses on the specific needs of indigenous Mexicans who have migrated to California. Across the United States these indigenous migrants are isolated even more than other immigrant groups. They speak neither English nor Spanish and are often looked down on by Spanish-speaking Mexicans.

They may not be the Spanish-speaking migrants that politicians picture when they discuss immigration reform, but as their numbers increase and trilingual members like Miguel organize, they have their own stake in the fractious debate in Washington. A possible language requirement would be particularly difficult for indigenous communities. Without Spanish, their road to English fluency will be that much harder. Their own languages are not traditionally written languages. Many have not had formal schooling.

At the extreme, an inability to speak Spanish and English can lead to tragedy, as in the 2010 case of Jaminez Xum, an indigenous day laborer from Guatemala who was shot and killed by Los Angeles police officers after he did not respond to English and Spanish commands.

People of the Rain

In the 2000 census, 407,000 people nationwide self-identified as Latinos of indigenous origin. In 2010 the number was 685,000, the most recent statistic available. "That's a 68 percent increase," said Jonathan Fox, department chair of Latin American and Latino studies at the University of California, Santa Cruz.

Migrants from Mexico's more than 60 indigenous groups have been coming to the United States for decades, but their numbers and proportion in the larger Mexican migrant population have increased in recent years. In addition to California, where they number at least 200,000, Fox said large populations can be found in Texas, 90,000; New York, 53,000; Arizona, 39,000; and Colorado and Illinois, both with about 25,000.

Very often, indigenous people come from a world apart, which adds to the pain of adjustment. Their communities have historically been cut off from the greater Spanish-speaking population of Mexico by their geographic isolation in rural areas and their lack of Spanish language skills.