I do think that people immigrating to a new country should learn the country's official language. It's part of what makes us a country, a group. Having said that, it's ok if you speak whatever you spoke in whichever country you lived in prior to moving here as well.
The U.S. English Foundation supports the idea of English being our Official (and only) Language, but to their credit they've done a great job mapping who speaks what where here in the US.
Living in NYC, it's really apparent that there are many languages spoken. Looking at the information on where I grew up, though, was interesting. 38 languages spoken! In descending order: English Spanish, Italian, Serbocroatian, Polish, French, Russian, Vietnamese, German, Ukrainian, Arabic, Chinese, Bielorussian, Korean, Gujarathi, Hindi, Tagalog, Japanese, Romanian, Albanian, Urdu, Pennsylvania Dutch, Greek, Welsh, Hebrew, Yiddish, Thai, Slovak, Dutch, Swedish, Portuguese, Mon-Khmer, Cambodian, French Creole, Hungarian, Swahili, Turkish, Lithuanian and Norwegian. Who knew?
Check out your hometown: U.S. ENGLISH Foundation (þ: Bookslut)