I live in downtown Seattle as well but currently just have a tie down at BFI for my M20F. I like only being 15 minutes from my plane and I have managed to fly almost every week including during the winter. S50 is a great place for social aviation as johncuyle mentioned join FATPNW (Flights above the pacific north-west) The founder and headquarters is at S50 in the north enclosed hangers. On FATPNW there is a long list of fly-ins this summer that will make it easy for you to explore the area.
Do pay close attention around S50 though, there's lots of traffic in the area. To the east is one of the main training areas for the local flight schools, just north of the field traffic IB/OB to RNT usually flying around 2000-2500ft just east of highway 167 and traffic IB/OB to Boeing flying just over the highway or a little west of it, and finally a lot of traffic flying east-west just under the bravo shelf around 1500ft. ADSB is a nice thing to have in the area.