I would suggest visiting in October, but more closer to the end of the month, after Columbus Day.
I visited WDW in October 2007, from Oct. 20-26. For the most part, it was very enjoyable and relaxing experience. The temperatures were very warm, upper 80s, some humidity, with lows in the mid-to-low 70s. About mid-week, though, a cool front blew through. It rained a little, and temps were in the upper 70s and lows in the mid-60s with overcast skies. That, and a little EPCOT Food and Wine Festival didn't heart either.
I arrived on a Saturday, stayed off property for a night in Kissimmee, and then checked-in at the Shades of Green, across from the Polynesian. Crowds were not too bad Sunday, when I went to the Mickey's Not So Scary Halloween Party.
Unfortunately the Palm and Magnolia golf courses were closed while the PGA moved in to prep for the Walt Disney PGA event, which was held the first weekend of November.
Monday through Wednesday it was pretty dead at WDW and at Universal. Sure, some of the more popular rides had long waits at all the parks, but I noticed Thursday and Friday (the day I left), the crowd surge was big.
I went by myself on the October trip, so it was interesting being in the single stand-by lines or being a lone rider and getting to quickly go through the lines (Everest and Rock n Roller and Tower of Terror and Test Track to name a few).
On the Tuesday of my trip I went to Universal with a friend of mine and practically all of the rides had a 5-minute wait, TOPS. My friend was shocked since he lives in Central Florida on the Spacecoast. He visited Universal in the summer with his son and the wait for, say, The Hulk or Spider-man and others were EASILY an HOUR or more.
I noticed that the Mission:Space wait times went up from 20-25 minutes to easily an hour or 70 minutes by Friday. The same can be said for Soarin'. So, if you go Friday-Sunday, expect some major wait tmes.
Best of luck and maybe I will see you in October 2008. I might need to schedule the trip before the golf courses shut down, but then again if I go closer to Halloween I still can play a round of golf, but it'll be over at the Pete Dye course or the Lake Buena Vista course.