For our October 2006 trip, I booked SSR (our home resort) at the 11 month window. On a whim, I called and was able to change to BWV's, and did not call have to call daily, just called and got the change. It was a one bedroom.
Not sure if you just want the EPCOT resorts for the F&W fest, or specifically want BCV's.
Also - we are have gone in September (it can still be very hot) and October (same). We love that time of year because it extends our summer a bit. You can definitely swim, weather in the 80's (september was 90's).
As for the parks, I did not find them to be overly crowded. Even the F&W fest was no big deal. We made sure to go during the week, as I have heard that EPCOT gets crowded on the weekends for the F&W Fest.
Good luck - Fall is a great time of year to go