At the traffic light by MGM there is a gas station, and the entrance to the BW. Continue down that road, underneath a tressel, and the BC/BCV entrance will be on your left hand side. A little bit further down the same road, again on your left, will be the entrance to the YC.
We always turn onto Epcot Resorts Boulevard (off of Buena Vista Way) at the stop light. You pass the Swan, the Dolphin, then the Yacht Club, and then the Beach Club. I assume it's just a big circle.
Thanks so much for your replies. One time we did go past the BW parking lot and under that trestle, so I know where you mean. I didn't realize YC/BC was there at the time.