A word of advice...we went last year Sept, 2007 for the free meal plan and the reservations for the restaurants were already hard to get in May. Basically, everybody is eating on the free meal plan!
If you think are going to go if they offer it during the same time frame, I would recommend going ahead and booking the more popular restaurants. I believe you can make them as much as 6 months in advance. You can always cancel them later. You don't have to have a room reservation in order to make dinner reservations.