Its been my experience over the last several years that its easier to get a bus at ANY time of day (early or late) from ALL STAR, CARRIBBEAN BEACH or other "distant" resorts than it is to catch one at WL.
I assume its due to WL having fewer guests AND its having at least SOME "alternate" transportation options.
Some of our "loneliest waits" at WDW have been waiting for a bus to ANYWHERE from the WL in the late evenings (and then it usually goes over to at least one other resort before heading to its posted destination).
AGAIN...
Before you choose to WALK...
ask if any of the busses "going ELSEWHERE" (like DAK or the Studios) will stop at WL, THEN go over and stop at say, the Poly, before going to its posted destination.
Riding one of these (and exiting at a Monorail Resort) would sure beat the early-morning WALK!
And yes, there are some very early-morning busses rolling.