When I said tight schedule I meant that I could not afford 2hrs over a meal. That having been said I dont want to spend entire trip on autostrada and would like to see countryside. Will be returning the following day on autostrada by quickest route.
The place I had provisionally earmarked is Enoteca La Saletta in the lower town but your suggestion is good if travel up and down from the upper town does not take too long I will try it.
I am not stuck to Certaldo and can lunch anywhere en route but preferably nearer Pisa given a departure time from airport of 1pm.
Am hoping to try local cusine and not surrounded by tourists.
Thanks again for recommendation.