The busses run constantly and it seems like there are always a lot of them going. If you can walk into the lot and pick-up place, then you should be good. I've been when lines to board are long but they move pretty quickly. My experience with the Toy Story lot is that the car traffic getting into it can be awful. It gets really backed up. For that reason we avoid it always in favor of Mickey's lot (I feel it's better organized for heavy traffic most of the time). The busses drop you in the main vehicle esplanade which puts you at the security check then into the main courtyard for both park entrances.