Foz de Iguacu is a city of around 300000 people, and although it has an international airport it is pretty small. From memory, it has about seven gates- all on one level. Transport into the city centre is easy via public transport. Buses cost 1.85 reals and run every 20 minutes. Buses from the centro go also to the National park which is another four kilometers beyond the airport. Just check with the driver whether the bus is going to the "centro" if you are uncertain.  The bus fare is paid to the conductor who sits about a third of the way down the bus. After he has been paid you then can pass through a turnstile to get to the seats- not too easy if you are loaded with luggage. The bus terminus on Avenida Juscelino Kubitschek has a Tourist Information Office where they speak excellent English. To reach it however you have to pass through another turnstile!. Taxis from the airport should cost around 35-40 reals.