traveling the west coast, hitching Washington, Oregon and Cali

I started hitching backwards with the east coast and the south and did the pnw last and I was amazed at how easy it was. You can even walk on the highway in Oregon. Wish I learned the ropes out there instead of the east coast.
 
Don't let the anti-hitchhiking signage on certain on-ramps scare you off. (A thumb in a red circle with a red cross through it)
Never had an officer stop and talk to me about it being illegal.
That's because it's not illegal, as long as you're hitching before that sign. Those signs mean no hitching past that point, not that hitching is illegal.

Some useful general advice: You can get down about half the coast by public transit, so if you get stuck, look for public buses. I'd take the bus from Seattle to Tacoma, then from there to Olympia; hitching out of Seattle can be a pain. Once you're in Oregon, it's legal to walk and hitch on the interstate (illegal in WA and CA). Avoid I-5 in California; you're generally better off on highway 101. Most of the towns along I-5 in CA suck, although you can make fast time on the freeway.