Since things can get off schedule due to traffic, having to load a handicapped party onto the bus.... my best guess is about 20 minutes from most places to all star.... except Animal Kingdom figure about 10 minutes or so...
When I stayed there in 1999 in the off season, it was about 30-45 minutes to get to the MK...
MAny people use the busses w/o incident, but we opted to go for a car, once we got stranded for 2 hours at the TTC bus stop after being the last ones out of MVMCP. So we just go with a car now. We'd rather spend the time in the parkinglot trams than spend it waiting at the bus stops. And, we won't get stranded again (unless the car breaks down). The price is usually around $150 for the week.
It's about 15 minutes for MK and DTD. Epcot and DS are about 10 minutes. And AK is only about 5 minutes. However this is once you leave the all-stars. The time to load at the other all-star stops will add time to the trip depending on how many are getting on/off and if there are any wheelchairs. Also keep in mind that the bus to DTD will stop at Typhoon Lagoon on the way back, and the bus to DS will stop at Blizzard Beach.