Most people in these parts seem to have done their US flying in Florida, so a search on that will give you much of whats been written here on that subject. However, since I'm such a helpful little pilot...
You do not need an FAA medical, nor do you need an FAA license before you get there. However, to fly an N reg aircraft over there you will need to get an FAA license issued to you, which is valid only whilst you have a valid JAA medical and license. You can get your FAA license from an FAA Flight Safety Office for free (or from certain FAA instructors for a small fee) but YOU NEED TO HAVE VALIDATED YOUR LICENSE WITH THE FAA before you do this. This requires you to fill out an FAA form (see their website) AND to fill out a CAA form, as they will release your details to the FAA. Assuming all checks out, the FAA will post you a confirmation letter which you have to present when getting your FAA license. Officially allow 60 days for this - although I'm told in the UK its often much quicker.
I'm assuming here you just want to fly on your current license/rating. If you want to take instruction for the purposes of gaining a new rating then you will need a visa - see the sticky in this forum.
Re aircraft, well take your pick. If you're going hot and high best get something with a bit more grunt (C172SP), otherwise a plain vanilla spam can will do. Don't forget rental prices are about 1/2-2/3 of what they are over here (possibly even less since theŁ has strengthened), so how about splashing out on a warbird or chopper flight?
I allocated 6 days flying over 8 days. Given that I spent most of day one f*rting about getting my license and getting checked out, I was really only on my own for 5 days and the pace was quite brisk. A week might be a little short, if you want some proper r'n'r.
I flew in central Florida, which is flat as a pancake but extremely easy to get around. Flying out west around the mountains is, I guess, more fun, but you need to be careful re mountain flying and awareness of the effects of altitude. My FBO thought New Orleans was reachable with an overnight stop, I think it was a about 4 hours flying time away in a C172SP. My trips were less adventurous, averaging about 100 miles from base.
Enjoy - its a very easy place to fly!
