As someone who's worked in the public relations field for many years, let me explain something to you. Marching with Mexican flags is not the best way to get the American citizenry behind your cause. In particular, flying the Mexican flag above the American flag (with the American flag hung upside down, no less) is a really bad way to make your point about deserving (and wanting) to stay in the US. You've got many good arguments on your side: you need to make them. Talking about "La Raza" isn't going to help you in the court of public opinion.
The Cranky Insomniac