We didn't want/request the WP, but we booked at 8 months out. We had to be flexible with our date to get the exact places we wanted, but we also wanted to get married on a Saturday at 5PM. I think if youre flexible with day and time of day you can do it!
I booked at 6 months out without any problems but we aren't going with the WP either. I was able to get the reception/dp locations that we wanted... but i was a bit nervous unit we signed the contracts!
We booked about 5 months out and had no trouble either! Like the PPs have said, unless you have your heart set on a Saturday night at the Wedding Pavilion or a popular date (12/12/12), you should be fine if you can be flexible.
I got lucky...I got the date I wanted at the venues I wanted (WP and GF ballroom) 5 1/2 months out. The only problem I had was that there was only a 7:30 time slot left. Which ended up being fine.
I was offered the WP 10 months out for a 10am ceremony. They offered me three different reception sites and although I wouldn't have initially thought of it, I'm absolutely in love with what we decided to go with (Backstage Prop Shop).
We booked about 10 months out and I knew I wanted the WP, but since it is a destination wedding for everyone involved and everyone would have to travel, I didn't care what day or date, and so we ended up with the date on a Sunday, which we love! Also, we wanted a morning slot for the lower F&B minimum and it was no problem. One important aspect for us was to take into consideration when the value seasons are for the parks, because having the wedding then made it even more affordable for our guests and many more are staying in moderate and deluxe rooms than we thought!