I know if I were doing this trip, I'd focus on a bike that is suitable for offroad as well as road touring, that has 26 inch wheels, and which has a parts mix that is easy to fix and replace in the middle of nowhere. This is may be out of your price range but the bruce gordon rock n'road tour ex will give you some good ideas of what to look for in a bike: http://www.bgcycles.com/rocknroad.html