Take rain gear.
My favorite is the Avenue of the Giants in N. CA. It's impossible to guess what else because there's just so much but a slow ride past San Simeon on your way up toward Big Sur is always nice. Lots to love about Carmel and Monterey. Half Moon Bay is pretty fine, too. Nothing better than planning to cross the Golden Gate after dark so you can soak in the city lights.
Coastal Oregon is like another world, rugged and fabulous, take your time and you'll see unbelievable beauty. A stop at the Lewis and Clark monument before you cross the mighty Columbia is pretty cool.
If you have time, a ride out onto the Olympic peninsula to the Dungeness Spit is fascinating and Port Townsend is pretty neat too.
