I absolutely love Seattle. I have heard great things about the San Juan Islands. Is it easy to get to the San Juan Islands without a car? ( I know there is a ferry but once on the islands, is everything pretty walkable until we get bikes?)
When we went to the San Juans, we went without a car. We did drive to Anecortes, though, to park by the ferry. We had no problem at all walking our bikes on the ferry. When you arrive on San Juan, the city (Friday Harbor) is very conducive to walking and there are several bike shops you can rent from. You may have to do some calling ahead, though. Once you get your ferry ticket, you can 'island hop' for free! Orcas Island has some nice biking, as well as San Juan. We went in July a few years ago and the weather was gorgeous!

Happy vacationing wherever you decide to go!