I have always heard that turkeys won't come downhill to respond to a call. However, I killed a big turkey last year that was walking down a hill behind me coming to my call. So the questions is will a turkey typically avoid coming up or down a hill?

I think that the preferred setup is to be above the bird, but, of course, there are plenty of examples of times when turkeys have gone downhill in search of that lonely hen, winding up as the featured guest at Thanksgiving, yours included. I think an overlooked aspect of calling from above the turkey is the quality of the calling sound. I've been above and below other hunters making hen yelps , etc., and I thought they sounded better when I was below the caller than when I was above the caller. Although it seems odd to observe that sound goes up better than down, in my opinion I think that the turkey below hears a better turkey sound from the caller above because of this aspect of how sound travels.

Another aspect of setup that I still think matters, in addition to your placement relative to the bird on a vertical plane, is the sun's location, especially early in the morning on a cloud-free day. (I want to be North or East of the bird.)