What the hell? You're citing stories and movies? Most did not in fact 'study all night long to learn english as quickly as possible to melt in'. Immigrant communities throughout US history are notorious for sticking to their own customs and languages. Not to trot out the oh so famous quote from Ben Franklin, but it's a good example:
Does that sound like a group intent on learning our customs ASAP? Franklin had the same short sighted concerns that people today have, and he was just as wrong. First generation immigrants often never learn their adopted language. Real assimilation takes place with the second and third generations. For example take this study:
http://pewhispanic.org/files/reports/82.pdf
English proficiency goes from 23% in the first generation to 94% by the third. Seems like they want to learn our language just fine to me.