If you rent, try to rent the same model you use at home, and bring your own set of sanitary parts (the horns and tubing). The sanitary parts are not rented, they must be purchased for each user, so you should be able to save at least around $30 by bringing your own with you.
Hospital lactation centers in the Orlando area should be able to rent you a pump, but be aware that a lot of pump rentals operate on a monthly basis, so you may be paying a pretty steep price. If you will need to transport the milk home via air, you'll need to check it. Bring along some hard bottles with hard tops (NOT the Avent rubber tops!), and also a supply of paper lunch bags and a cardboard box. Put the milk in the the lunch sacks, mark with your name and room number, and put them in the box without sealing it. Take the whole thing to your hotel kitchen and ask them to store it in their deep-freeze during your stay. They can add the add'l bags daily. Before you leave, take the whole thing to Kinko's and have them box it in an aircraft-approved frozen food shipment box. (Call ahead to make sure they have the right packing materials on hand when you arrive.)