We walked to Epcot almost every night last month from The Dolphin. It takes about 15-20 min. depending on how fast you walk. Maybe 10 min. if you speed walk. The Swan is only right across the walkway from The Dolphin so the same from there. It was sometimes faster to walk to & from Epcot than to take the Friendship boats, they stop at Yacht Club, Beach Club, Boardwalk & MGM, depending on which boat you get.
The walk to MGM is another story. We did it once & never again. It took us a good half an hour, probably more.