For the most part people park at the parks,the International Drive area does have the I Ride Trolley which goes from the Vineland Premium outlets south of Sea World north to the Internal Drive Premium outlets north of Sea World.I don't believe it goes into Universal,I think you would have to get off at the stop by Wet n Wild and walk the bridge over I-4 to Universal,probably a 15 minute walk,there are other hotels walking distance to Universal,maybe the Holiday Inn or Hyatt Place by Kirkman rd but that Road has pretty good traffic,obviously not as good as staying at a Universal hotel.For Sea World and Aquatica you could take the trolley or stay at a hotel by the parks,I've stayed at the Hilton Garden Inn and that hotel as well as the Rennaissance are literally on the other side of the Sea World parking lot,all you have to cross is a calm small street,from the Sea World parking lot you can take a shuttle to Aquatica.Busch Gardens is like in the middle of a neighborhood that aside from Busch,the waterpark and some hotels is not very touristy,I really don't see where I would leave my car outside the park,stay at a hotel right by the park,I believe there's a La Quinta right by it.As someone said look for a pass for the Busch/Sea World parks that might give you free parking.
