In reply to gazhbo: Tendonitis is a bit of a bastard unfortunately. If it is just in your wrist you may still be able to do press ups and bicep curls as long as it doesent aggravate it (not really recommended tho). However if its in your elbow youre screwed exercise wise.
Rest for as long as possible. When you actually get there strap it up to climb. Stretch every day the week before you go, but not on cold muscles. A shower will warm the muscles, but after exercise is better. And you may have to scale back the goals a bit. Most important of all, warm up really thoroughly at the crag, i.e Walk in to raise the pulse, some VERY easy traversing on big holds to wake up the arms, then stretching, then a couple of really easy routes, then a bit more stretching.
But all is not lost! It may be that by the time you go it will have healed up completely. Five weeks should be enough time to fix mild tendonitis as long as you dont start messing around with it. If it is fixed just take it easy, its better to do two weeks fun climbing than be pissed off for thirteen days when you f*ck it up on the first day. You'll know how much you can do when you get out there.....
PS. To complete my completely non medically based rehab, get a bottle of MSM, find some suitable stretches and strengthening exercises and when you start climbing again, go easy on the crimps.