We did the whole coast in 3 weeks last year. My only recommendation is to travel southward. Almost everything you want to pull off for is between the highway and the beaches, getting out again going north can be a hassle.
If you're at all interested in architecture or airplanes, don't miss the Tilamook Air Museum. The airplane collection is all kept in flyable codntion and the building is amazing. Going from memory here, its over 300 feet across, almost 200 feet high and 1700 feet long. There are NO internal pillars and it's made entirely of wood, except for the hangar doors and their supports. In WW2, it was a base for US Navy airships and the building could hold six fully inflated ships.There were two hangars originally, housing 12 airships, but one burned down when it was being leased to a farmer who stored hay in it. Spontaneous combustion in the hay was the cause.