The All Stars ___SOMETIMES___ share buses, but not during the busiest weeks. We've stayed at the All Stars several times, and usually the only times that buses are shared is during the afternoon, when not as many people are riding.
Buses usually depart approximately every 20 minutes, and the time it takes to get to the parks depends on which park you are going to, because the parks are at different distances from the resort. Generally it takes about 15 minutes from the resorts to the parks, sometimes less. Always plan 60 minutes just because you may have to wait for a bus to arrive or something. And right now there is a lot of road construction around the resorts.