Speak to the club you end up at, they will tell you where the nearest FSDO is.
You used to be able to turn up and fill in a form and hey presto 10mins later they issued you a restricted FAA licence (restricted to any endorsements on your UK licence - i.e. no night flying until you get the NR).
Since 11/9 you have to make an appointment to do the paperwork, if you turn up on spec you will be turned away.
Best bit is is that the licence issue is FREE!!!
Julian.