Marin!!!

Not that I am biased!

The Tiburon loop (Paradise drive around the peninsula of Tiburon) is a classic relatively easy ride.

Also Riding in the Nicasio/Western Marin area is great. If you drive to Nicasio, you can do a relatively easy ride out to Pt. Reyes Station and back, avoiding most hills if you go Platform Bridge Rd.

Get a Krebs map of N. SF Bay area and explore.

There's planety of great riding in Marin that may be a little tougher than what it sounds like you are looking for, but those suggestions are good places to start and work your way up.