We stayed on the 5th floor of Dolphin's East Wing last summer. There is a walkway between the Dolphin and YC unless either resort has made changes in the last year.
You can take the East Elevator to the bottom floor (not the lobby) and then just follow the exit signs to a side door that leads to the outside. You do have to walk around the lake, but we enjoyed seeing the baby ducks there. I think you can also take a stairway down to the door also, but we didn't do that since we had a stroller.