Great question, although I can't answer you directly, I do know that if you are driving down, Disney advertises on billboards about their Welcome Center in Ocala. They say you can get stay on Disney property with big discounts. The idea is to get those travelers who are uncommitted to stay at WDW.
I have often been tempted to try this, but I just can't force myself to drive that far and NOT know where I will be staying and I wouldn't want to drive around looking for a place to stay.
We have on our trips heard people asking about availability when were have checking into our hotels, and they are always quoted a higher price than we have paid with planning ahead. Too many discounts to be found on the web.
Good luck, if it works out for you give us a report. Maybe one day I'll go commando style and just head down there and see what happens.