Yes, my up close and personal opinion is that assimilation is alive and well. I encounter it every day. Most service workers in Orange County are Hispanic, and they speak very servicable if not fluent English. Many come from somewhat middle class backgrounds in Mexico actually.
Then tell me why there are boatloads of Spanish-Language format stations on the Los Angeles are radio dial? Why are nearly half of the local televisions stations aired in Spanish? Why does L.A. have a lot of graffiti? Why is there a considerable contingent of individuals who wish to revert the American southwest back to Mexico, or at the least, Aztlan? Why were American players spit on and booed at a US-Mexico soccer game at the LA Coliseum? Why are many groups, particularly Mexicans, displaying their colors everywhere you go?
While some are assimilating, many are not.