I have been to WDW in October two times, once in 2015 and again in 2016, for the Food and Wine Festival and the Halloween Party (and the free dining promotion). While I enjoyed both trips, I probably won't go during that time frame again. The weather was still very hot and humid. One trip was affected by a hurricane and the other had travel impacts bc of another storm system. In 2016, we went the first week in October thinking the crowds would be lighter. Wrong! Apparently everyone else had the same idea LOL. Magic Kingdom was a zoo both days we were there. We ended up leaving early both days and napping at our resort so we could go back at night with less crowds. We did the Halloween party and it was really crowded - fun but very crowded. Epcot had usual F&W crowd level although the humidity made it too hot to eat everything we wanted. I don't remember crowds being bad at AK - just the oppressive humidity. My friend went later that month, closer to Halloween, and she said the crowds were even worse. I really don't know the slowest times to visit anymore. We still really enjoyed our trip though. Just go in expecting large crowds and you won't be disappointed. We went in August in 2012 and the crowd levels have really increased since then. Our best trip, by far, was the first week in March 2014. The weather was fantastic!! I wish it was that nice when we were there middle of March this year LOL. A lot of people were there during Mardi Gras, and the Canadian's spring break, but we had gotten there after a runDisney race and a federal holiday but before the large spring break crowds. That trip was so magical!