Uhaul rental one way from Portland to Astoria is cheaper than a one way rental car. Bus (greyhound) is also a possibility, but the schedule didn't work for me, and for two people the cost was almost a wash. I think it was $90 for the uhaul rental.
I took the bike on the plane with me, assembled it in the airport, rode to Uhaul (3 miles), got the truck, picked up my partner at teh airport (he had a later flight than me), then we drove to Astoria. My tour partner had his bike shipped to the hotel. THe next morning i took the uhaul the 2 miles into town with my bike in the back, then rode back, while my partner assembled his bike in the hotel room. It's easy to just call a hotel and ask them to accept the bike in advance, they are used to cycle tourists there. I think the hotel was named Hilltop or Top of the HIll, or something like that. THis is also a good way to ship stuff that the airlines won't let you take on the plane, like stoves and fuel cannisters - just UPS to a hotel.
It was nice to have a hotel for the first night, as the exitement level and logistics complicated things enough that camping would have been a burden, rather than fun.
have a great ride!