You cannot guarantee a room in toy story, but we have stayed there three times and each time we have been lucky enough to get a room overlooking Andys Room in the toy story block.
What we did was firstly on the occassions when we booked through a
travel agent or Virgin was give them the request which they add to the booking form, which they will send to the room controller at All Stars Movies about one to two weeks before you travel.
Secondly I faxed the room controller at ASMo one week before arriving and also the day before arriving. The content of the fax was basically not a demand but a begging note! lol I wrote that while we appreciate that they cannot guarantee requests it would make it such a special holiday for the children etc, but I did start it off with as we are travelling from the UK such a long way etc
We visited over Thanksgiving and Christmas so busy periods and got what we wanted, I just told my children that I had made the request but did not hold out much hope so when we got the rooms it made it even more special. The amusing thing is that last christmas we actually requested a room number, when I checked in the staff apologised they could not give us that room, but had given us the one next to it and apologised, they had given us another room feet away but where apologising!
I wish you luck, but we are considering going at the same time so don't take our room!!