You can take a bus from the "Settlement" to MK, but it's not a Direct Bus. The Yellow Line will go to the Settlement (internally) and then from there it goes to the Wilderness Lodge (so yes Cait8383, you can take a bus to the WL). From there, however, if you want to go to the MK you can either walk down to their dock and take the boat (which seems silly unless you just wanted to see the lodge) or Transfer from the Fort's "Yellow" line to the bus that goes between MK and WL. Taking this route, however, is generally MUCH longer. We have done this twice (well actually going the OTHER way from MK to WL and then back to the Fort). First time was because they stopped running the boats one night (not sure what the reason was) and we were re-directed to the buses. The second time was this past August. It looked like nasty weather was coming and there was lightening in the distance and DW didn't want to be on the water if the storm came in.
Both times, the "Wait" to transfer at the WL was about 20 minutes or so. So plus the additional wait time (at the other ends of the routes depending on direction) it can be significantly longer to "Bus" to the MK.