You can book before the discount is released. When it is, call right away and request it. If you don't do it right away, the might run out of discounted rooms. But we've always done it that way and have only once (when we waited a few days past the release of a discount) not gotten our room with the discount. We did it that way when we booked our hotel for spring break. We made the reservation last summer for a theme park view room at the Contemporary. We called when the discount was announced, and they applied it (25%, I think) to our room.