The easiest way for us is to take 417 (South exit, already been told), but stay on that road until you go through the Welcome Arc on that road (it turns into 536). After you go under the arch, take the 2nd right exit toward Wide World of Sports and I think MGM is on that sign, too. This puts you one Lake Buena Vista Dr. Then, at the 3rd light (Victory Way) you will see a fire station on your right, turn LEFT. Follow it around, and you will see the Pop entrance at the first light you come to.
If that sounds confusing, I'm sorry. That's just the fastest and easiest way for us.