There is a ferry boat that goes from Downtown Disney to Old Key West (it's the same service that also stops at Saratoga Springs). You catch it from a different jetty to the Port Orleans service though. The DVC resorts ferry dock is by Pleasure Island, while the Port Orleans one is next to Rainforest Cafe.
Andre
The last time I ate at Turf Club over at Saratoga Springs, I took the boat from the dock there by Rainforest Cafe. It went direct to Saratoga Springs and back. As you walk down to the boat dock there behind Rainforest Cafe and Cap'n Jack's, the line on the right went to the PO resorts and the one on the left went to Saratoga Springs. They didn't share with Old Key West at all.