Conversation so far:
What languages are/were spoken by the Indigenous people of mexico?
The Law of Linguistic Rights of the Indigenous Languages recognizes 62 indigenous languages.
What are the most popular (or a few of the most spoken) language(s) from the 62 indigenous Mexican languages?
The only single indigenous language spoken by more than a million people in Mexico is the Nahuatl language.
Are there culturally different people residing in different territories in Mexico?
In 2015, 25,694,928 people in Mexico self-identify as being indigenous of many different ethnic groups.
What is significant or unique about the ethnic groups and or their culture in Mexico?
Mesoamerica was densely populated by diverse indigenous ethnic groups which, although sharing common cultural characteristics, spoke different languages and developed unique civilizations.

Question: What indigenous language did they speak?
Self-contained rewrite: What indigenous language did the indigenous people of Mexico speak?