I would probably ride it in the right tire track. When traffic approached from behind, if the lane was definitely wide enough for a safe pass within the lane (i.e., lane width greater than 14 feet), I would squeeze right to let traffic through within the lane, but only if I was convinced that such passing was safe, and I would go back to the right tire track after the motor traffic passed me. If motor traffic was heavy and impatient and the sidewalk was clear of debris, I would consider taking that, but it wouldn't be my first choice. I suspect that there are few pedestrians on that stretch.

You should probably find out what the local laws are concerning riding a bicycle on the sidewalk.