"I've spend a fair amount of time around a LOT of people from Mexico; never heard it (or of it)."
Maybe they didn't want to tell you about it, or you didn't ask the correct questions.
Nope your wrong, Mexicans don't actually speak Spanish, they claim to speak Mexican.
"I didn't know that, either. I thought most people in Méjico spoke Spanish; after all,
their national language is Spanish. Incidentally, ours isn't English. So far as speaking Mexican goes... there's a bunch in indigeonous languages, there's probably even a few Nahuatl speakers somewhere near what's left of Tenochtitlan"
YT - Next time you get a chance to stop in Mexico, drop by one of their bookstores, and ask for a "Spanish into English/English into Spanish" book. You will be amazed to find that they sell "Mexican into English/English into Mexican" books
instead. Now why would that be? Unless they didn't feel they spoke Spanish, which was the language of their conquerors.
Or speak to the "common" man. The reason is because a lot of the Nahuatl/indigenous words are incorporated into their language. Mexican is spoken by 90% of the population. The Spanish language is spoken by 10% of the population, primarily their political elite (as in white Mexicans, descendents of the Conquistadors, or European immigrants).
Now why would we want to recite the American Pledge of Allegiance in Spanish?
"You might not want to, but others might. It sounds nice, and I can. We don't have a national laguange in this country, after all (unlike Mexico)."
I wonder why you would recite something written in English in a different language just because it sounds nice. Usually something is lost in translation.