Outside, no. Never. It's almost as hot here at night as it is during the day. Also still very humid at night, so you can still sweat in the summer after the sun has gone down.
Having said that, there is one reason you may need a light sweater: air conditioning! I'm a lifelong Floridian so my blood is pretty thin, and I freeze in restaurants & theaters because the AC is always cranked up (down?). I have a little black sweater that goes everywhere with me. If you're really sensitive to cold like I am, you may just want to have a little something to throw over your shoulders when you're inside. Probably not a big bulky sweatshirt (although I've brought one to sleep in if the AC is too cold in the hotel room), just something with sleeves.
Hope this helps!