Nope, buses don't run to MGM or Epcot. But, I know that before I actually went there, I just couldn't get my mind around how this 'walking' would work. So, for those of you who are wondering and aren't familier with the lay-out of BW/BC/YC resorts and their proximity to Epcot and MGM....There is a small lake. On one side of it is BW, the other side is YC/BC. If it were a clock it would be BC/YC at 12, BW at 6, Epcot at 3 and MGM at 9. There is a canal that runs from Epcot, past the edge of BC..into the lake. Then it comes out of the lake by BW and goes down to MGM. There is a walking path all along the lake and canal. You can walk from BC to Epcot in about 5 minutes...quicker than walking and then waiting for the boat. You can get to BW in about 8 minutes. It's about a 15 min. walk from BW to MGM, along the canal.
The boats are nice to take in the heat/humidity or if you have little ones who just too pooped out at the end of the day. But, they are pretty slow and make a lot of stops...so you most likely are better off just walking. If it is rainy, the boats are covered and are really comfy.