The San Juan Islands are a hop, skip and a jump away from Seattle. I took a trip with friends to explore Lopez Island over a September weekend. It was a beautiful adventure - the foggy island mornings were enchanting and rosy sunsets over the Sound felt magical.
We ferried out on a Friday afternoon from Anacortes (you should book your spot on the ferry in advance). It was a 1.5hr drive from Seattle, then about a 45min ferry ride.
We camped at Odlin Campground, only 1 mile from the ferry terminal. It was a peaceful spot, partially on the water and partially wooded. They had drive-in campsites as well as walk/bike-in. I took Burt, and we had a perfect spot by our friends who were tent camping.
We took a ferry to Orcas Island one day to whale watch and check out the vibe. We didn't get too lucky on the whale adventure, but we did drink some great cider at the Boat House Cider Works. The "Cascadia! Hops in Cider" was phenomenal!
We now know that you really have to time your ferries in advance - otherwise you may end up waiting for the next boat for up to 3 hours... Word to the wise, plan in advance! :)