Central Florida Hobbies is the longest standing (and only real remaining) model shop in the Orlando area I think.
http://www.orlandohobbyshop.com/
They won't have much racing stuff in stock but they can get anything you need/want within a week. I always call in when I visit - been going since I was a kid!
Unfortunately there isn't much Off road racing in the area these days (although they have an on road track at the side if Kissimmee Golf club, recently held a Nitro worlds I think).
There is a big indoor track and shop near Cocoa Beach if you wanted to take a drive that way (Space Coast RC/Superior Hobbies). Superior Hobbies used to have a store in Orlando but it closed earlier this year and moved to the coast.
HTH