Are there ZTL's in any of these three cities?
In Assisi, we would like to park in lot #C, the underground parking garage at Piazza Matteotti.
In Cortona, we would like to drive to the top of town and park at Santa Margherita Basilica, then drive down to Piazza Garibaldi and look for pay parking spots, and if none, drive down to the free lot on Viale Cesare Battisti.
In Montalchino, we would like to drive to the Fortezza and park in the pay lot.
Would we be going through any ZTL's?
In Assisi, you'll be ok if you come up the hill from Santa Maria degli Angeli via Viale Vittorio Emanuele II and Via Umberto I (i.e., the eastern flank of the city) to Piazza Matteotti. That way you bypass the historic center altogether.
Here's a website about the Assisi ZTL (in Italian, but you can run the important part through Google Translate)
Sorry, don't know about the other towns.
Park at the bottom of the hill in Cortona and take the bus or taxi up to the town.
I would not drive through the narrow streets of Montalcino. Not sure about ZTLs there but by the time you get there, there may be even if there are none today.
