I had people say they were Christian, but it was usually so they could get rid of us, not many asked real thought provoking questions.
I have a good friend that did try and talk to JW's when they came to her door, ask questions and when she found out I was raised a JW asked me why they never came back!
I think for the most part, the average JW doesn't know how to engage people in real meaningful conversations at the door. They are given presentations with the express purpose of getting literature in their hands, not to discuss bible topics.
BB