The only two cities that I am aware of having had defensive measures are Mayapan and Tenochtitlan. Mayapan has a stone wall encircling the majority of the city with dispersed settlements extending out beyond the walls. You can see just how large the city is in this LiDAR map. While Mayapan had stone walls, there is little evidence of any warfare taking place at the city walls. Numerous amounts of arrow heads have been found just inside the walls which have been interpreted as stockpiles of arrows in case of attacks. It sort of looks like Mayapan never really needed to use their walls before the city succumbed to civil war and was abandoned in 1480.

Tenochtitlan's defenses, since it was an island city, consisted of raising portions of the causeways that connected the city to the shore. The only account I am aware of these being used was when the Aztecs fought the Spanish, but that is outside the scope of Postclassic. If you don't mind going into the colonial period, I could go further into the siege of Tenochtitlan as well as discussing the fortified peñoles in Jalisco/Zacatecas during the Mixton War of 1540.