Your sleeping bag need not be waterproof. If you want to save from buying a whole new bag then consider using a goretex bivy sac over the sleeping bag. That's what I use. Keeps the sleeping bag dry and still breathes to allow moisture out.
The only exception I might point out is the southeast area where water is really a big concern. In those cases, 1) you really want to try to keep your bag dry, and 2) avoid down! You want something that you have a chance to dry out without a dryer and doesn't totally lose all its value if wet.
Oh, and if you plan on camping, you need a pad to keep you off the ground.
-john