Puget Sound/San Juan Islands/Gulf Islands.
We have easy anchoring, usually in sticky mud and rarely in more than 30' of water. Lots of towns to visit, lots of water for sailing, lots of parks on the water with trails for day hikes. Easy to get into many of the anchorages even when arriving late. (Except that August gets REALLY busy in the San Juans)
Our summer doesn't usually start until July 4th.
It's usually nice through September.
We know have 88 resident Orcas (a new baby was spotted yesterday). I see porpoise several times a year and there is even a Humpback hanging out south of Seattle right now.
We don't get a lot of wind here. The most I've been in was 25 knots but the usual is more like 0 to 10 so don't expect a lot of time spent with the sails up.
I don't know about marina costs because I always drop the hook. State parks put out mooring bouys that you can use for $10/night. Many parks also have docks that you can tie to for a small fee. Washington State offers a yearly pass. The cost is based upon the length of your boat.