Bob Fry writes:

Most of the Mexican nationals in the US are poor country people from
northern Mexico, but even they have learned the basics of reading and
writing their native language.

No, they have not. Most of them are illiterate, in Spanish and in English.

In most countries, in fact, the rural population tends to have low rates of
literacy.

Do you even know any of these people?

A few. It's hard not to when living in certain parts of the U.S. I also know
college-educated Mexicans who can speak real Spanish, and read and write it as
well (and of course they also read, write, and speak English).

--
Transpose mxsmanic and gmail to reach me by e-mail.