Definitely bring a good jacket for cool to cold whether. Plan for very windy/chilly evenings. In the afternoon, the days can be nice and warm, even hot. We are going in March for the 3rd time in a row. The previous two years have been hot, warm, cool, and chilly!!! So, my advice, is to at least prepare for a cold night or two. For us, we were caught unprepared the 1st time thinking that Florida would be warm or at the very least confortable. Boy, were we surprised to find it cold!!!
I live in Houston, Texas and our weather is similar to Disney, but even we were surprised at the change.