Thanks for the superb info and advice! Much more than what I was expecting.

Based on all of this, I'm thinking I might wait for late May, and then ride from Troutdale to Cascade Locks or The Dalles ... assuming I'm able to talk somebody into coming with me, and moving the car while I ride. If I can make that work, I'll stick to the Oregon side; if not I'll consider a loop going back on SR-14 in WA.