insta, i'd highly recommend the county park campsite on the west side of San Juan Island, an absolutely beautiful location with a view of Vancouver island and the Olympic Mts. Did some riding on Orcas,too, but not as good - the road from Eastsound over to Moran State Park is not especially enjoyable due to fairly heavy traffic. There's a San Juan Islands recreation guide that shows all the roads and is quite useful.
Time permitting, taking the AMTRAK Cascades to Seattle, and the Victoria Clipper passenger ferry to Friday Harbor is a hell of a lot more fun than driving I-5. It does cost a bit more, but well worth it.