Medea...re-read his first post. He said his parents' FRIENDS do not know how to speak english, not the parents themselves.
And yes, learning a second language becomes much more difficult after kindergarten or so. There's an area of your brain (Brioca's area) that deals with speech production; if you learn two languages while young, your brain will contain a single Brioca's area. If you learn a second language while older, you will have two (or one for each language that you know). What does this mean? In younger children, the language learning process is more inherent in the brain, and the end-result is a smoother transition between languages. When learned at a later point in your life, the languages must "speak" with one another in a more complicated fashion, and thus more effort is required.
Then again, to answer your question about how they've survived this far without learning english: Look around you. There are more than enough ethnic areas in every major city to compensate for poor (or no) english skills. I work in a hospital ER, and you'd be shocked to see the number of patients that I see every night who possess absolutely no english skills. Of those, a few state that they also do not have any friends who can speak a word of english. Now that is a scary thought...living in a country in which you nor no one you know can speak the prominent language.
My own personal thoughts on this matter: make english America's official language, and require that immigrants know at least basic (i.e. mediocre conversational) english before being granted admittance to America. Should they not know English, offer them the opportunity to re-test after a few months in the country. If they fail a basic english skills test after that period of time, deport.
Though even if English were not chosen as the official language, we should decide on one eventually. It would make things a tad be easier, methinks.