Maya is the first language of the people of Santa Maria Poniente, and their ability to speak Spanish varies widely by age, gender, and amount of time spent working on the outside. I've met people who couldn't speak a word of Spanish, those who understand it but can't speak but a few words, and people who speak so well you would never guess this is a second language they picked up as an adult.
The age and gender stratification is really interesting. Older women are the least likely to speak Spanish, since they've neither had schooling in Spanish as a child or worked outside the village as an adult. Older men have worked on the outside, but were never taught Spanish in school, so their ability varies widely and by effort. Younger women have been schooled in Spanish but don't normally leave the village, so the Spanish fades with age. Finally, younger men and children of both genders are the strongest Spanish speakers, since they have constant reinforcement from either school or work.
At the moment, school is taught entirely in Spanish, but there's a popular policy proposal on the table to make Maya mandatory in every school in Quintana Roo. The state of Yucatan just passed a similar law, and its looking very possible that it will happen in Quintana Roo as well. Its one of those rare political moves that could single handedly rescue and entire language and culture form slow, generational extinction.
Variations of Mayan are spoken in four Mexican States and in four countries, so I doubt very much that it could ever go completely extinct. Compared with Mayo and Yaqui, the native languages of Sonora (where I'm from) spoken by a few thousand people each, Maya is in a pretty good place.
Local extinctions, however, are entirely possible, a fact that the Mayans of Santa Maria seem keenly aware and afraid of. I've heard horror stories about other villages were everyone speaks Spanish, about kids who come back from Cancun refusing to speak Maya, about young men who speak perfectly well but are ashamed to use the language of their parents. The good news is that there's also a lot of Mayan pride, a relatively recent effect that is just starting to kick in.
* Picture is of Cecilio Yam Can, who speaks pretty good spanish and learned as an adult.
** I'm reposting this to better reflect the chronosequence. Sorry for the repeat!