Winter Summerland is on Buena Vista Drive. Take the main exit out of DHS and at the traffic light, turn left onto BVD. BVD bends around to the left after you cross World Drive. Winter Summerland is on the left, and Google Maps has you go past it and make a U-turn to get in.
The directions below appear to show the route that a bus would take from the loading/unloading area. The buses merge in with car traffic near the exit and before the intersection with BVD. Follow the perimeter road counterclockwise on the map and you'll see where it merges with the road that the blue line follows. Just make sure to get to the left after you merge. You're coming in from the right, and after you go around the bend I think there are two lanes going right and possibly a lane going straight, so you have to cross three or four lanes of traffic to get where you can turn left at the light. I'm having trouble getting street view to work, otherwise I could tell you right from the map.