I hired a taxi driver with his cab for the day several years ago. I do not remember the cost, but it was rather inexpensive, and the drive was so friendly and helpful that he almost doubled as a guide.

He took me across the border from Argentina into Brazil and back with no problem or issue whatsoever even though I did not pay for a tourist visa for Brazil. No one checked.

I was able to spend several hours at my leisure at the bird sanctuary and the falls on the Brazil side.