I voted 70-80. I like above 80, if the humidity is low. You know how steamy it can feel in Florida, although I think I could get used to that year round!
We went in May a few years back, it was so hot and the humidity was high too, it was in the high 90's most of the time. There were nearby forest fires and we could smell the smoke from our hotel. We went to Epcot one day and spent all our time inside so we could be in the air-conditioning - phew!
I voted for 70-79. It's not too hot, and not too cold for me. Not only that with that temperature range, there would be a lot of characters walking around the parks, since it wouldn't be too hot for them, either. I should know! I went to WDW last summer, and nearly passed out, because of how hot it was!!! It was in the mid-90's with a heat index of over 100 degrees!!! Ouch!!!
At least it won't be that hot on my next trip, since I'm going in the last weekend of March, and the highs should only be in the mid to high 80's!!! Yay!!!