I don't know about POP but at Port Orleans the cabs were waiting there. It took 30 seconds for them to pull around to get us. AND that was a van since we needed a large vehicle.
If you take the DD bus and then transfer back over to the Boardwalk area, I would just grab the Boardwalk Inn Bus. It really depends on where you are going in the Boardwalk area. The Boardwalk Inn/villas is the closest to the "activities", restraunts, piano bar, Espn. But if you are planning on walking all the way around the lake, you could take a Swan/Dolphin, Or Yacht and Beach club. However, the boat ride from MGM is quite pleasant too. Again I would get off on the last stop BWI if you are looking for the "boardwalk area".