Always bring more water than you think you will need. Avoid drinking from streams or lakes because of the potential of giardia. Padded biking gloves are great, both for padding from the bars and when you use your hands in a fall. In colder weather, add polypro liners or try cross country ski gloves. Chamois bike pants are very comfortable.
Some brands even have hip padding for protection in falls.
All-terrain biking shoes. Optional, but they improve biking efficiency significantly and give you more stable platform when riding downhill. Also, expect weather to change quickly in the mountains. It can be hot, dry cold and wet in one day. Storms move in quickly and leave just as fast.