How to prepare for the big trip?

I often think about what to do to prepare for our exchange.
At first it is important, that all the formalities are managed. But luckily for me Mr. Denefleh and Mrs. Humrich do manage most of that so I just have to fill in some slips of paper.
But what about the language? Will I understand all the Americans? And is my English good enough to comunicate?
I read all the material about America Mr. Denefleh gave us, but I don't feel well enough prepared.
I try my best to improve my English. I'm sure I will improve it in America, but I'd like to improve it before we are in America, too.
So what shall I do? I thought it would be best to read some books watch some movies in English. Therefore I startet to read Harry Potter in English. But if you've seen the movies a million times and read all the books in German it gets a little boring.
My mom wants me to prepare well, too. Therefore she bought me some books in English.
To be honest, I did not read them all. But I try my best to be prepared, so that I can enjoy my time in America.

Maybe you've got some great tips for me?