disneymouse,
If you do not want to use a park admission, then the MGM route is the way to go. If you take the monorail to EPCOT, you must walk through Future World and then part of World Showcase to get to the International Gateway. This is where you would exit for the BC.
The boat ride is slow but enjoyable. It will take about 15 minutes. You stop first at Swan and Dolphin and the the YC/BC.
As posted before, you can walk from MGM to the BC and it will take you about 20-25 minutes. The walkway is on the same side as the bus drop-off just past the info booth on your left. Keep in mind, however, that the majority of the walkway is not covered and if it is a hot day, the walk becomes very long. My vote goes to the air conditioned boat. That way you are not exhausted by the time you get to breakfast.
As far as for allowing time, I would say at least an hour. You have to take into account how long you will have to wait at WL for a bus to MGM. Then you have to hope that a boat is at MGM (they run about every 15-20 minutes). Anything less than an hour and you might not make it.