I would go in February or April,lots of breeding and mating going on. But in reality, any month is a pretty good month because the birds are so much more approachable at any time compared to northern climate birds.
Gail
First of all, if you are planning on photographing birds in Florida, Ding Darling is no longer a prime location because of changing water levels. I also wouldn't spend too long in Everglades National Park. Go into this forum and look at the old threads and posts. You will find a LOT of information there.
I agree with Gail on February through April. However, good bird photography in Florida continues right into the summer, especially for nesting and chick photography. Once you read some of the threads below, let us know what more specific questions you have.