If your flight arrives on time, you should be at baggage claim by 3:15ish. Then, you will have a wait of up to 15+ mins for the bags to come out...I know others have had good luck but I'm always standing there with the others that have waited 20 mins for their bags, so I always put the 'worst case scenario' times in. Then, down to DME..about 5 mins. Maybe 5 mins in line, checking in, then off to the bus lines. You could be in a line that is getting ready to board so you won't have a long wait. But, if your bus has just pulled out, it could be 20 mins for the next one. So..lets say 10 mins there, at the bus line, then 10 mins on the bus before it pulls out. (These are pretty much the times I have had on at least 4 trips with DME). Then 30 mins to POP. So....that puts you at POP checkin at..4:15 or so. Then, checkin may take up to 20 mins...POP seems to take a bit longer than other resorts, not sure why. Now, it's about 4:40, off to your room. Spend a bit there, get back to the MK bus by 5:15. If the bus is there, great, just hop on. IF not, you may have to wait up to 20 mins for the MK bus to get there. So, we'll go with a wait of 10 mins..now it's 5:30ish. You'll get to MK just before 6:00.
I can't imagine it would be much sooner than that....of course, you could luck out and have very short wait times all the way along. I always try to imagine the 'worst case scenario.'