If you know when you are going, I would book as early as possible so that you are sure to get what you want. October is obviously not the busiest time because the kids are in school, but the Food and Wine Festival is a big draw.
I just tried to book a studio for the weekend of the 21-24, and there was nothing available. I did not expect to get anything, but figured I would try. Wanted a quick weekend in WDW.
Again - book as early as possible. I am sure you can still find rooms available most times, but better safe than sorry.
Eric