She actually learned to ring the bell pretty early. She got to the point where if I stood a few moments at the door with all the dogs standing there waiting to go out she would ring it. However, tonight I was on the computer, heard the ring and saw her standing by the back door. I let her out and she went straight out and peed. Success!
I had heard of others teaching their dogs this but never really gave it much thought. Me and my guys have a pretty good routine and most of the time I'd be letting them out a certain times during the day anyway. Occasionally one might whine or pace at the door if they have to go at a "non-scheduled" time. Any pups and fosters simply fell into the same routine.