Adam,
Yes, they are. Admittedly, the Movies and Sports All-Star resorts are the furthest away from each other, with the Music All-Star resort wedged in in-between them. And you do have to walk through some parking lots, but it can easily be done.
If you want to see the exact layout, you can get a resort map at the unofficial site, www.willcad.org. You can see the three All-Stars laid out together on each individual resort's maps, in the lower left corners. That should give you a layout idea.
And if you are going to be doing it often (because of rooms at both resorts) you can see what buildings to request at each resort to shorten the walk.
I hope that this helps. Feel free to send me any follow-up questions!
Have a magical vacation!