I don't think I'll be going over any lava beds. Although in Oregon you never can tell. I just need versatility. I think a cyclocross with gnarly tires would do the trick. Then I can switch out the tires for road-exclusive tours.

Mycoatl, I'm going to Lewis and Clark as well, but for undergrad. Thanks for the tips on Portland and fenders--I had that suspicion when I visited the school earlier this year and they had had rain for 30 straight days. I hear they call the rain "liquid sunshine" up there.