Must you park only in lots outside the walls of San Gimignano? If so, can a person in good health push a wheelchair from the parking lot to the center of San Gimignano?
You can only park outside the and pushing a wheelchair will be a challenge. It's uphill and I believe, cobblestones.
John, I just looked back at our photos from our trip and there are no cobblestones, I was wrong. In fact, the road / walkway is smooth tile - I don't think it will be that bad for someone in good health to push a wheelchair.
I'm looking at our pictures. The streets are stone but they are reasonably smooth. There is an incline into the center of the town but it may be doable. If you want my pictures to see for yourself, send me a PM with your email ID and I'll send you several that show the main street.