Best place for cold cuts in Zih ?

Aren't preservatives such as nitrates, which add to color and flavor, an integral part of "cold cuts"?
Without them the shelf life would be minimal.

Correct. However, if you plan on consuming the meats quickly, this is not an issue. That is why I adore markets such as the Mercado Municipal. That meat is butchered for you that very day. Before refrigeration, it was common practice that one would visit the local markets almost daily. If you can rouse yourself out of bed early enough, visiting the docks for the local catch from the fishermen is a must-see when in Zihuatanejo. It does not get any fresher than that!