What's with all these "Well, you COULD take this and walk there and then go here..." kind of answers?
You COULD walk from home, but I wouldn't recommend that either.
The SHORT of it is... If you want to go from MK to MGM (Studios):
A. From MK: Take Monorail or Ferry to TTC.
Take the "Studios" Bus to the MGM front gate.
B. From MK: Take Monorail to TTC.
Cross-over to Epcot Monorail, exit at Epcot
A few yards up the sidewalk from exit of the Monorail down-ramp (walk OPPOSITE WAY from Epcot gates) is Bus Stop for "Studios" Bus. When it arrives, ride it over to the MGM front gate (short trip).
C. From MK: Stroll down to MKI bus-loading area. Take a Resort Bus heading for Swan/Dolphin (it goes to other resorts in that area, too.)
Exit Bus at Swan or Dolphin, stroll down to the boat-dock and take a Friendship to the Studios (its the next stop on the boats going in that direction.)
You CAN walk from Swan/Dolphin/Y&B Clubs/Boardwalk to MGM Studios (takes about 30 min.) if you want.
If you'd like lots of EXTRA walking, there are plenty of "out-of-your-way" detours (see other posts) you could also choose.