I had never visited a place with three borders. And I can say that the experience is quite peculiar because you will always have three options to do anything. Your choices will depend on your pocket and your willingness to cross borders and stamping your passport.
To visit the Iguazu Falls, one of the seven natural wonders of the world, you can arrive by plane at the international airport of Foz de Iguaçu (Brazil), Puerto Iguazú (Argentina) or Ciudad del Este (Paraguay). You can also arrive by bus to the terminal of the same cities. Just look at the cost-benefit ratio between the value of the tickets and hours of travel.
The three cities share an international public transportation system, so you won’t have problem to move around by bus from one country to another. It will be like going from one neighborhood to another because cities are pretty close to each other. The only thing that is kind of boring is the immigration at the borders, but it’s nothing out of this world. Just carry with your identity document (for Mercosur) or passport (for other countries).
Taking this into consideration, and if your passport has space for a few more stamps, you can find a hostel or couchsurfing in any of these cities. (Read more about where to stay here)
To exit from Foz airport take the 120 Aeroporto/Parque Nancional bus (US$ 1, 17) . It goes to the TTU (Terminal urban transportation) in the center of Foz. In the terminal arrive and leave all buses to anywhere in the city, you won’t need to pay for the second bus, while you take it inside of it. So once you find it, you will never be lost.
Also, outside the terminal you can take buses to the Argentinean and Paraguayan side (US$1, 70). Ask for the stop that is next to a food truck.
At the airport and in the terminal, there is a tourist information points to pick up maps and ask for directions.
Going to Argentina (Puerto Iguazu):
Take the bus Argentina / Puerto Iguazu (US$1, 70). They will give you a ticket when boarding, keep it. You will have to get down on the Brazilian immigration and do the exit of the country. Then with the ticket, you can take another bus (from the same company or associated) without paying again. However, the same bus company can take up to 30 minutes to come. You can board any bus and pay the US$1, 70 again.
Upon arriving in Argentina immigration you will have to do to enter to the country. But in that side the bus will wait for you.
During the weekends many Brazilians go to the Argentinean side to party and shopping. Hence you can get a lot of traffic in the late afternoon during those days.
Going to Paraguay (Ciudad del Este):
Again, at the bus stop outside of Foz terminal, take the Paraguay / Ciudad del Este bus (US$1, 70) This bus crosses the border without stopping at the immigration. Or you can take a bus into the terminal to go to the bridge (do not cross the border) and you can simply walk.
The traffic between Brazil and Paraguay, the bridge of friendship, can be chaotic. Crossing the bridge by walking or by moto-taxi is a good option to not get stuck in traffic. If you take the bus that cross the border you won’t be able to get off the bus until you reach the other side of the border, so if you get stuck in traffic you’ll lose a lot of time. So my recommendation is to cross the bridge by foot.
There are also direct buses between Puerto Iguazu (Argentina) and Ciudad del Este (Paraguay). Taking less time because there is no need to go through the terminal of Foz (Brazil).
Read soon what to visit at the three borders. Also see some tips on where to stay and how to save money on accommodation.