From I-4 westbound, take exit 26B and follow the signs carefully. At one point you will need to be in the left lane to avoid ending up at Epcot. Or from highway 192 take World Drive straight north to the toll plaza. Both routes are clearly marked.
At the Magic Kingdom toll plaza bear to the right. The far right lane is for Disney buses. The next lane in is now set aside for cast members. So aim for the third booth from the right. Tell the attendant you are going to the poly.
When leaving the toll booth stay to the right (don't follow the traffic into the parking lot ahead to the left) and follow World Drive through the intersection with Vista Blvd. At the next light (Seven Seas Dr.) turn left. You will pass between the TTC and the MK parking lot. The Poly is next on your right.