The first generation immigrant from Mexico will learn English as a second language. Their children will learn Spanish and English. And their grandchildren will only speak English. It has ever been so, and so it will be. English is the language of assimilation in the US, and immigrants want their children to learn English! Mexican immigrants in California have repudiated the ESL programs in the public schools for English immersion programs.
Have more faith in the worth of your culture! It is the culture that created the greatest nation ever to exist on the planet. And the greatest freedom and prosperity for the individual. That is why so many Mexicans are coming here to work and live.
Cinco de Mayo is quite a holiday for Anglos in the US, in case you haven't noticed. They don't know what it's about, but it's a great excuse to get drunk.