While it is not air conditioned, there is a quiet walkway in MK, it runs between Space Mountain and Toontown. If you are in tomorrow land, walk up to SM, near the aracde and follow the Speedway on your left. The train will come by periodically, and a few families wander back that way, but it is usually very quiet. Also, in less crowded times, if the upstairs areas in Columbia Harbor House or Pinnochio Village Haus are open they can be more private too.