Vashon - went to scope out the bike riding - mm meh, it really doesn't look like a great place to ride; for one thing when you get off the ferry you are immediately faced with a monster hill. I hate hills right at the start of rides when I'm not warm. Then once you get to the top, the rest of the island is pretty flat and pastoral. The shoulders are not great and there's a lot of fast traffic. Most of the route slips that I've seen take you on a loop around the island, around the west side and then back on Vashon Hwy on the east. That's fucking retarded, Vashon Hwy is awful to ride on, just do an out and back on the west side. There is one real nice bit of twisties for driving around Cedarhurst but otherwise pretty meh.
West Snoqualmie Valley Road in the Duvall - Carnation area. Way too much traffic for fast driving. Narrow road and no shoulder - does not look like a nice place to bike at all. Scenery is pretty good though - you get views of the Cascades and pastoral river valley farming stuff. It's an enjoyable sunday drive.
A bit further north of there you can do High Bridge Road and Woods Creek Road. Both pretty nice drives as the traffic is a lot lower; these are popular with local motorcyclists, so they may slow you down, and cops do watch them. Again not great bike rides, though Woods Creek might be okay despite lack of shoulder because it is pretty low traffic.
Snohomish is a pretty abysmal tourist trap, but there are still some decent sights there. There seems to be a hot air balloon launching every time I go by it.
A bit further north I hear Menzel Lake and Jordan Road are good, but haven't been up there yet. Also Mountain Loop Hwy up to Silverton - Bedal looks cool, but I think it's pretty rough dirt road through the highest part.
Renton - Maple Valley trail. This is a "rails to trails" conversion, so it's all flat, separated from the road. On a nice weekend it might get unbearably crowded near Renton, but the traffic thins out and it gets more scenic as you get closer to Maple Valley.
Green River Gorge Road / Green Valley Road - this is some pretty rural Washington. Not great for driving though, around the Gorge Road area the pavement is in really abysmal condition, so you have to slow to watch for killer pot holes, and then in the Valley area it's residential and trafficky so you have to / should take it slow. Gorge Road area seems promising for biking, though there are quite a few sport bikes and ricers and such joy riding out here so it may be a bit dangerous. The gorge itself is pretty fucking rad, really deep shear cliffs down to rushing river, but it's hard to access (the small shitty state parks in the area don't provide any access to the good parts of the river); I hear that the locals know the access paths and guard their secrets.
There are some very promising driving areas further afield (mainly in the Mt Rainier - Mt St Helens area) but that will have to wait for summer.
It's sort of weird that it's easier to get away from people in San Francisco than it is here. Part of the issue is that SF was really amazing about saving wild land right near the city (the whole of Marin and the Peninsula). But I think another part of the problem is the Cascades. It's nice that we have the Cascades right here, but there are basically no roads in them, and even very few decent hiking trails at low elevations. So essentially we are trapped in a little strip of land on the west side of the Cascades and almost every bit of it is developed and suburbanized.