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.
Actually, Hispanic immigrants are holding onto Spanish far longer than earlier immigrants held on to their languages. In this, they are aided by the forces of multiculturalism, both in government (bilingual education) and out of government (the programs that ask whether you want English or Spanish). Earlier immigrants were not coddled like this, and they also faced an eventual end of reinforcements from the old country, both of which assisted their assimilation.
A prime offender in this, of course, is Bush, who insists on addressing Americans in Spanish. One could only imagine what Teddy Roosevelt would have thought of one of his successors addressing Americans in a foreign language.