The quickest way, in my opnion, is to Valet park at the Yacht Club. If you valet park(for a fee) at WL and use your car to Valet park at the Yacht club you do not have to pay the Valet fee again(within the same day). This works as the quickest way to get from WL to the Dolpin. When you enter the Yacht Club just walk strait through the lobby and then make a right and go over the bridge to the Dolphin. I feel this plan has 2 advantages and 1 disadvantage. Advantage 1: you are parked for the day at an Epcot resort with easy access to enter and leave Epcot for the entire day. 2: the walk is just a little longer ( ok more like 'regular' longer) from the Yacht Club than the self parking at the Doplhin but soooo much more senic! The disadvantage is cost. Valet is $6 or $7 for the day and the tip(optional but usual) is around $1 per pick-up/drop-off.
We use this plan to save time also. About 1 hour saved from having to use Disney transportation!
Enjoy ~ Debbie