I went in late June and it was really cold! Be advised that in the border of Brazil and Argentina you need to get out of the Bus to get your passport stamped, I was able to get back into the bus but I imagine that if for some reason you are delayed in the stamping process your bus may depart. To clarify, this is when you are a crossing from Brazil to Argentina. Also the lady at the bus station in Puerto Iguazú told me that the to get in to the Park (the Falls on the Argentina side) they only accept Argentinan Pesos and no USD or Reales or even credit cards! I was really surprised and ask her twice in Spanish to be sure about this, so because I didn’t have pesos, I had to go to an ATM, but the closest to the station didn’t let you use a debit card supported by the PLUS system, in other words your US issued credit card will not work there, so I had to walk to the other side of the town till I got to the National Bank where I was able to get some pesos. With all this I lose the bus and had to wait for the other one. I knew that there is an ATM machine in the Park but knowing that sometimes you cant get money out (as it happened many times in Brazil) I was not going to take the risk of getting there to learn later that the ATM doesn’t accept my card.
On my way back from the falls I thought that the bus was going back to the main bus station, but the bus just pass in front so you need to be watching carefully otherwise you will end up in other part of the town. I tried to squeeze a visit to the Brazilian side of the falls that same day but the last bus going or stopping close to Foz do Iguacu Falls was already gone by 2:30 (aprox).
Although it wasnt as easy as I thought, going to Puerto Iguazu from Foz on my own (at least for me) it was well worth it, since nothing compare to the beauty of the falls. it was probably the highlight of my trip.