Just booking some tickets for our family trip in June.
The best prices I found where at themeparkticketsdirect.com.
I find it is better to buy before you go, but I suppose on how long you are going for?
If you're only going for a week, then by the time you do the essentials: Magic Kingdom, Hollywood Studios, SeaWorld, Universal Studios, Islands of Adventure (each one will take about a day), you'll only have 2 days to rest!
If you're going for two weeks, then you have some time to catch your breath.
Magic Kingdom & Hollywood Studios are both Disney - you can buy tickets at the gate for these. Last year they where $85 per adult, per park. Remember car parking is also $14 for the day.
Universal & IOA - I think the best value for this is the 2 park bonus ticket, at €91 each, for unlimited access to both parks for 14 days. Again there is a car parking fee. The new Harry Potter section might be open by May, so expect it to be busy.
SeaWorld tickets should be bought directly off the SeaWorld website, and atm, are $69 per person. BIG TIP: if you hold onto your ticket, and get it validated at the ticket centre, BEFORE you leave the venue, you'll get a second day free!
I've never been to Busch Gardens, too far away, too much else to do, so can't help you there.
It might be a good idea to "Theme Park" it one day, and have a day-off the next, maybe doing a bit of shopping or other sight seeing. The parks are soooo big, you'll be wrecked!
We're all heading out on June 5th, if you're still around, we can meet up for a beer!
Anything else I can help you with, just ask.