It is a tropical city: humid and hot. Lot of insects, so get yr insect repellant ready. U will see lot of homeless kids, is a very sad sight.
However, I don't feel unsafe when I was in Puerto Iguazu. It is very different from Pantagonia or Buenos Aires where living expenses are super high. If u like humming bird remember to check out the Jardin de los Picaflores (bring insect repellant too!)
Visiting the falls from both Brazil and Argentina is a very different experience. Highly recommended to make the effort, spend another day and visit the other side too!
The only interest is to visit the waterfall. Than you have to escape from the poor and dirty Argentina city.
The food cost terrible and all the other services costs very much. If you want to shop anything go to Paraqui.
except the waterfall,the others place not valued to visit.i prefer u go to brazil instaed stay in this town