I've heard that February is a great time for herping in the glades from a handful of people. But there are a lot of factors you have to consider. If going in the summer, expect rain showers at least once a day. This can be both a good thing and a bad thing. Heavy rain can sometimes mean little to no reptile movement (thats the least I could say for amphibians.) A little rain shower in the late afternoon or night time can get snakes moving around.
I would personally say that early summer or late summer would be perfect for snakes/frogs. Your best bet would to road cruise in the summer. Hot summer days could mean no snakes, just lizards and gators, but road cruising after a hot day will almost guarantee you a snake on the road.
Hot days = hot roads at night (snakes will go on the roads to soak up some heat for the night)
Small rain showers = these get herps moving around.
I went in june and had amazing luck road cruising. Ill post the link here...
http://herpingwithdylan.com/forum/index.php?topic=921.0