The spa tour is very brief--10 minutes or less unless you have a lot of questions. You will basically see the rainforest and fitness center, locker room, look into the hair salon and "treatment" area, and be given a list of services/prices, etc. You are then able to make any reservations you'd like. You'll also be given a schedule of fitness classes.
I did sign up for the rainforest after seeing it. There's nothing about seeing the locker room/treatment rooms,etc. that would change my mind about spa appointments. Basically, you're either going to do them or not.
I believe that our tour was shortly after lunch. That's when they are up there making appointments.