You will love the holiday decorations at these resorts!!! They are beautiful. You can do it two different ways, depending on what else you have planned for the day. If you are in MK that morning, you can take the BW bus back to the BW. Then, just amble around the lake, stopping in each resort along the way. Then, you can either hop a bus at any of the resorts for a different park. If you are going to Epcot that day, just exit WS between UK and France via the International Gateway. Then, again, walk around the lake viewing the resorts.
You can walk from MGM to the BW area and then continue along with your plans. You would find it easier to start in a park and then hop a bus to BW/BC/YC. Then at the end, hop a bus back to a park, or walk over to MGM (or take a Friendship boat) or walk through Epcot. But, walking through Epcot requires you to use a park entry on your passes. MGM does not, since you never have to enter the park...you just keep walking, past the entrance, to the bus area...from either the path from BW or from the boat dock.