Sorry you don't have more options, but the only way to get to Mk from MGM is by Disney bus transportation! I was there last month and found it very usefull. It's not the quickest way but it's the only way. Once you load onto the bus, they stay for others to board, only about 7 minutes. I'd have to say it's about a 10 to 15 min. drive to MK. If you wait to leave as the parks close, I can garuntee (SP?) it will take longer since everyone else has to catch the bus. I'd recommend leaving MGM 15 to 20 mins before closing to catch the beginning of MVMCP in MK.