Yep.
But keep in mind that it will cost close to $20 and it won't be any faster than just taking the bus to MK.
Well, it could cost more or less than $20. But it will be faster than taking the bus, unless you get the best timing imaginable. If you walk out the front door of, say, Beach Club, there will usually be a taxi waiting nearby. Max 1 minute to get the taxi called up. Then it drives you directly to the Contemporary at approximately the same speed as the bus, where there is an 8-11 minute walk to the front gates of the MK.
With the bus, you have a 2 minute walk to the bus stop, a 0-30 minute wait for a bus to arrive, a 3-4 minute wait while the bus fills up with people, potentially another stop at Boardwalk or Yacht Club, then a drive to the MK, where you have a 2-3 minute walk from the bus stop to the front gates of the MK.
So when everything is absolutely perfect, because you walk up to the bus stop just as a bus is just finishing loading, and there are no other stops prior to the MK, you would possibly save a few minutes because the bus drops you off closer to the front gates than the cab would.
In the common case, the bus averages 10-15 minutes slower. In the worst case, the bus could be 30-45 minutes slower, because buses are running late, or they have multiple stops before heading to the MK, or you're unable to get on the first bus because there are too many people.
In the off season, 10-15 minutes is not make or break, and not worth $20 to most people, I expect. But if bus service is having troubles, cabs or rental cars can save you tons of time.