Just one nay vote--a voice crying in the wilderness--against the Oregon coast. I'm crazy, I know, but I found the traffic load during the summer to be pretty ridiculous on many sections of the Oregon coast. We went during July, so sub-optimal I'm sure, but our experience was so negative, we vowed never to return. Up to about 10am, things were pretty nice. Afternoon riding was horrible with virtually constant traffic, thousands of cars, noise, etc. Scenery, towns, camping, indeed all excellent, but for actual riding, the cars ruined it for us. This is largely because there is only one way down, Hwy 101. In California, some stretches are indeed noxious, but I've ridden from Sonoma County to Santa Barbara three times, and much of this route is on Hwy 1 and other, quieter secondary roads, so the bulk of commercial traffic is on Hwy 101 a bit further east.
Obviously, lots and lots of people love the Oregon coast, but if you go in summer, you must be ready for some truly amazing traffic loads.