Various: Go to Foz!
I didn't hang out in Puerto Iguazu at night at all. From what I've read some of the hotels have entertainment during peak season (i.e. the Sheraton), but outside of that don't expect much here. But hey, you didn't come to this part of the world for nightlife, did you?
If you are able to, I'd suggest going to Foz do Iguacu in Brazil and hang out on Avenida Jorge Shimmelpfeng where you'll find quite a few good restaurants and great outdoor cafes. The perfect place for a chopp (draft beer) and some good conversation.
Cuba Libre bar.
There´s not much nightlife in Puerto Iguazu, but if you are looking for some fun, the bars and discos are located along Brazil avenue. I really liked the Cuba Libre bar, nice latin music for dancing; and the more modern Yoko Ono with chill out music.
Falls under full moonlight: Once a month
I took the full moon tour... Maybe many people will disagree, but it wasn’t that special. There are three shifts. I was in the first one (8pm). The moon looked yellow-orange, which was an awesome spectacle in its own (everywhere in the area). It should be rather exciting being at the jungle at night, but you’re on a train with lots of tourists, talking, laughing, shouting, taking pictures with flash. It’s impossible to listen to the jungle sounds or even to feel a bit afraid, which could have been fun. Maybe the other two shifts where better to watch the falls under the moonlight, since the moon was higher, brighter and more white. Maybe I wasn’t lucky. The full moon tour is a bit more than US$ 20 with transfer in and out included. There’s an option with dinner at the National Park restaurant for US$ 30. Get in touch thru www.iguazuargentina.com.
Dress Code: Confortable shoes and repelent.