Valley View/Orient Land Trust is the best in my humble opinion. Clothing optional, and expect a wide variety of ages and body types. A variety of pools of various temperatures. Some are completely natural, and require a short hike. Other pools are built up, but still very nice.
Very laid back vibe, more so than the more developed hot springs. You can rent cabins, rooms, camping spots, or just day-trip. Call ahead to make reservations, as they do fill up.