Hi, Christopher! One of the things I love about
Disney's Old Key West resort is that you can take the nice, leisurely boat ride, which, at the end of a long day, can be about the most peaceful thing at Walt Disney World.
Disney's Water Transportation hours vary, usually based on the times theme parks and
Disney Springs. The official word I got when I called Walt Disney World is the boats stop running at 11 P.M., although I know I have taken a boat at just about 11:30 from Disney Springs to Old Key West.
Buses run a bit later to Disney Springs.
Disney buses usually run until 1 A.M. from Disney Springs back to the resorts. You may be in time to take a boat over, but you might have to take the bus back.
I hope you have awesome weather and a wonderful time on your upcoming Walt Disney World vacation!