Youre leaving it a bit late... normally takes three months to organise.
Fax the FAA a copy of your licence, medical, and the last page from your logbook, along with the relevant form available on their web site. I cant remember what its called, but search it for "foreign pilots" and print that off.
Nominate an FAA district office that you want to go to, and when your application has been confirmed with your CAA of the issuing state of your licence, theyll call you in, you show the original documents to the guy behind the counter with a mustache (for some reason, they all have one) and he gives you a temporary licence.
Your real one comes out a couple of months later.
Its an absolute breeze to do, but get onto it about three months before you arrive.