By the time you have walked from the Dolphin to the Epcot monorail, you could have likely been on a bus to your destination.
The Epcot monorail is at the extreme far end of Epcot from the Dolphin, roughly a mile away. It's about a 10 minute walk from the Dolphin to the International gate to Epcot, and another 10+ minutes to the monorail. Then you may have to wait another 5-10 minutes for the monorail. At the other end you arrive at the Ticket and Transportation Center (TTC) near the Polynesian resort.
I would only recommend this for the following, and only if you enjoy walking.
-- Dolphin to Polynesian (e.g. for dining). Just walk from the TTC to the Polynesian; it's only 5 minutes. There's a good chance you can beat a bus this way as you would have to transfer somewhere. Even if there is a bus Dolphin-TTC, it probably makes other stops.
-- This may also be a reasonable way to get to the other MK resorts by taking a monorail or bus (to WL) from TTC.
-- An adventure when you don't care about taking the fastest route.