Katydid this an ongoing issue within the hispanic/latino community.
Some are quite offended by the use of the term hispanic and only wish to be referred to as latino/latina.
It's a very sensitive issue and I do agree with Amster that in TX one does not just label any person or child "mexican" because of the color of their skin. That just isn't acceptable. Because IMHO TX borders Mexico, and when you refer to mexicans you are refering to those that are citizens of that country not ours. Very subtle regional practices.
This is just my personal opinion and my personal experience.
(also if one moves and works within a predominately latino (my preferred word) community never ever make the assumption of the originating country of the ancestors. Calling a PR a Mexican can start the party off wrong LOL (all our latino members here will get that joke).