I've been wanting to get into mushroom hunting for quite sometime myself, but haven't taken the leap yet. Most hunters are reluctant to give up their spots, but I would recommend contacting the Seattle Mycological Society, they would probably be your best bet.
@SeattleBen a number of our employees in the Olympia REI store love to mushroom hunt. They often mention the Capitol Forest; you could certainly call the store and ask for their other favorite recommendations, just make sure you check here for rules and regulations about mushroom hunting around the Puget Sound. Finally, this might be a fun group to connect with! Happy foraging!