In parts of the country it's probably a matter of practicality. Doesn't make it right, but I'm sure it's the case.
Basically, I agree with Mtnbiker's position. I wouldn't ask anyone to give up their culture, but I do think it's fair for people, if they are going to live and work in a community, that they have a working knowledge of English.
On the other hand, I live in a neighborhood where there are many shops that only post their specials in Russian. And, no, I don't like that. It's not that I mind the signs being in Russian, I mind them not having English translations because it's like saying "well, we like it here. we want to live in your town. but we don't want to do business with you". Just seems kind of skewed.
By the time the immigrants have kids, though, language generally isn't an issue, since the kids are immersed in English once they start public school.