Boy, I can tell that gatorwoodie and CsTrFrK have never driven the capital beltway at rush hour. Seriously, while not a Floridian, I can say that I-4 isn't too bad if you avoid rush hour, which isn't too hard to do on a trip to Busch Gardens. Just try to scoot for Tampa right after rush hour in the morning, and then eat dinner before you leave the Tampa area in the evening. We did this and had no real trouble.
Do always keep in mind that central Florida is the official thunderstorm capital of the country and do everything with that in mind.