First and foremost, those folks that you are referring to will be offended if you call them Mexican. Unless they ARE from Mexico, many of them hail from central and south america and like to be rather referred to as Hispanic. Some people also refer to the entire spanish speaking peoples as the SPANISH which is also very derogatory. Its kind of like when someone calls me indian, and im like uhhhh NIGAA PLEASE.
But Hispanics in general are great folks. Don't value education as highly as we do, i must admit.
Edit: I also realize that Hispanic is also an incorrect term, but the most accepted on official forms and such. Since Hispanic refers to anyone with Spanish blood, it does not include anglos, afro, portugese and native american populations that live in south and central america.