Hey man, im from SF too!
Id say if want to get an idea of the best riding close to Seattle id go with this
(unnamed) - Seattle, WA. Take you all the way around the lake with a loop around Mercier island. Theres a couple of little climbs but nothing too serious. Very scenic the whole way. Kinda reminds me of the paradise loop. Lots of trees and water. And there are still plenty of places to make pit stops.
And like ceedbux said you can also do the Chilly Hilly if you want something a bit shorter (it think its like 30ish miles). After that anything else is going to take you pretty far outside of Seattle (like 100 miles) and im not sure youd want to do any driving.
The weather has been nice, so when you come up there should be lots of sun. But just like home, layers are the key.
