There are tons of RV rental companies on the web and you can pick one up in Orlando. Cruiseamerica is the best known. I can't speak from personal experience, but they had a bunch of them rented when I last visited the Grand Canyon, so somebody likes them!
But just do a search on Hotbot or Google for "rv rental" orlando and you'll get a huge list. Here's a few....
www.cruiseamerica.com
www.campertour.de/usa_elmo_transfer_orlando.htm
http://rv-rentalnetwork.com/d/request_step1.asp?AgentID=1
A couple of words of caution if you haven't rented before. First off, renting an RV ain't cheap. You can stay in most hotels for less. It really only makes sense if you just want the atmosphere of RVing or you're trying them out to see if you like an RV.
Second, make SURE you read all the conditions, particularly what's included and what's not. Many companies want to charge extra for plates, dining ware, sheets, bedding, etc. Some even charge extra to use the awning.
Make sure it either comes with insurance or that you're covered by your own insurance. Don't assume that a standard policy will cover an RV unless you add it temporarily.
Finally, make sure the dealer gives you a complete orientation of the operation of the RV. Pay particular attention to the LP gas, holding tanks, electricity and cable. Also turn on everything, including TV's, stove, cooktop burners, etc. Make sure everything works before you take it out.
Have fun.
