Ditto what Charlie said. Like all popular cruising areas the San Juans get busy during the best weather- July and August. The most popular places like Friday and Roche can be a zoo. While most of the islands have homes built on the beaches there are lots of good anchorages and many, many parks, some with mooring bouys. There is generally good holding ground for anchoring. You want to respect residents private property and privacy, but almost all the beaches are public up to the high tide line for good walks and tidepools. There are some islands that are private and they are posted, and also some marine preserves (Yellow Is). Use common sense and be VERY careful with any open fires, the islands are extremely dry at that time of year (they may look green but they are tinder dry) and most have limited to no fire fighting equipment. I would recommend buying "Waggoners" cruising guide as well as "Gunkholing" both have info. on all the "secret" anchorages and little known marine parks (there is one by us that frequently doesn't have more than one boat in it during August weekends). September is our favorite month for cruising, less crowded and still warm, but the San Juans are great year round. I would recommend that you venture into the Canadian Gulf Islands as well while in the area, even more beautiful IMHO. Have fun.
SV Laurie Anne
1988 Brewer 40 Pilothouse