Just in case anyone's interested...
I had my TURP procedure on 9/18, and was able to take a very brief ride yesterday (9/30) afternoon. Sitting on the seat wasn't an issue as I had feared, but after a short time pedaling I felt I was working my abdominal muscles too much at this point in recovery.
Tomorrow marks the 2nd week since my surgery. It'll probably be another week or two before I feel like I can do any distance without undoing some of the healing that's been happening, so I'll wait. But overall, the recovery is coming along faster than I'd hoped, and most of my worries about the procedure and its aftermath have turned out to be unfounded.
-- Sam