If you've not flown in the US before, then I strongly recommend you get a copy of "FAR/AIM 2009". £11.50 from Amazon UK. It's an inch and a half thick, but at the beginning there's a section where it says what you need to read as a PPL (a small fraction of it). Do read the recommended sections, as airspace, radio, circuit (or rather "pattern" in US terminology) procedures are all rather different in the US. Nothing dramatic, but it helps enormously to have read it before you arrive.