I say we turn this boycott on them and not just for one day.
Don't buy products made in Mexico, don't eat out at Mexican restaurants and phone in every suspicious illegal to the INS.
There is at least one Mexican restaurant here that is owned by hispanic conservative Republicans, and my late Uncle had such a place. Baby/bathwater. Not all Mexican restaurants are participating in this pro-illegal immigration stuff, and in fact, one Mexican restaurant in S. Texas that I know of is owned by some Chinese guys, so I don't think it's fair to hurt their businesses based on the kind of food they serve.
The only problem I have with boycotting Mexican restaurants is that I know of at least two that are owned by legal citizens and I doubt are backing this. Why punish all of them?