usually the weather isn't so bad in October here. However, last October was brutally hot (we've been having a crazy year in weather-terms!). So because Florida's weather is SO unpredictable, I'd bring both shorts and jeans and a sweater lol.
If you're thinking for dresses, you could always go for thinner material and bring along a bolero in case it gets chilly?
I got married October 22. It was soo hot and humid for the first 3 days (including my wedding day). Then a tropical storm passed through and it dropped into the 60s as highs for 3 days.
I traveled to Disney Oct 3-15 back in 2005 and it was in the 80s. We weren't prepared for the heat and made a mad dash to buy shorts. I would definitely plan on summer like weather
We were at Disney for this past Halloween and it was astonishingly hot. We were very surprised b/c when we went at the end of Sept '08 it wasn't nearly as hot.