Hi, I have been a member of http://disboards.com/
for nearly a year and been finding out soo much info about Walt Disney World.
I would defiantly book all restaurants before you go. The reservations open up 180 days before arrival date and MANY people booked at 180 mark!! It is very different to DLP where you can make a reservation on the day. Reservations for the signature restaurants will most defiantly be taken by the 90 day mark or before.
on the DIS forum, I regularly see posts from people who are disappointed that they cant reservations for restaurants after the 90 mark
I know its hard trying to decide where to eat, but unfortunately thats the way the system is in Florida