This is one of those issues I get annoyed with conservatives over: "Let's make English the official language of the United States." I strongly disagree. My reasoning is very simple: Do we really need another bureaucracy controlling how and what we speak?
I believe that every person coming to the United States should learn English. I believe they should do this for their own benefit. If I moved to Mexico or Spain, I would want to learn Spanish. If I moved to Japan, I would want to learn Japanese. If I moved to Australia or Great Britain, I'd want to learn as much as I could about the differences in dialect. Why? So that I could succeed as much as possible by communicating as clearly as possible with others. Good communication skills are a major key to success in any culture. Those skills start and end with language.
On the other hand, if we make English the official language of the United States, what will happen? Obviously, we'll need a special department to define what English is and how it must be officially used. How may it be taught in schools? When and how may other languages be taught? It will define rules as to when and where English must be used and have a list of possible exceptions (airport signs, traffic signs near the Mexico border, certain literature, etc.). Then, it will have to start defining penalties for violating those rules. Otherwise, what difference does it make if English is "official or not? I don't want to see any such thing happen.
If someone can show me how we can make English a requirement for learning without the bureaucracy to define the rules and enforce them, I'm not interested in seeing English become "official" in the United states. I believe it is in the best interest of each individual and society as a whole to learn English in the United States. yet, legislating such will certainly come at a higher than intended cost.