howdy sir Walrus, I also started in Astoria, flew to Portland and took a bus to Astoria. Although this was eons ago (94!), I'd have to say that Astoria down to San Fran is a really nice ride, very neat how the landscape changes. I only went a few days south of San Fran, so can't speak for the rest.
People I met and biked with had started in Vancouver, and a number of them said that the Washington state bit was kinda boring, and they would have skipped it doing it another time.
just do be prepared for climbing, it aint flat.