Not sure exactly how to explain it, but you can get more information from Concierge at your resort, the CMs at the ticket windows or at the turnstiles at the International Gateway.
If you take the boat over, the boat CMs can probably also point you in the right direction.
As you come to the gateway area from the Boardwalk area resorts, the water and boat landing will be on your right. On your left, there is a building that houses restrooms and inside the park, has a shop.
The rental area is in that area. I believe it is after the point of coming into the park thru Security bag check and the turnstiles, but am not absolutely positive (Im about 99.9% sure though, since ECVs and wheelchairs are not allowed out of the park where they are rented).
If you want to rent for the entire time you are at WDW, post 2 of the disABILITIES FAQs thread has links to some off-site companies recommended by DIS posters. All will deliver to your resort and pick the
ECV up again when you are done.
The rental area is inside the park. You go thru the bag check, then turnstiles and the rental area is far left on the inside of the park in between the store (inside the park) and the restrooms (outside the park). You cannot get to the rental area without going into Epcot.
