Hi, I am From Buenos Aires. I am a pilot too so I can help you.
You will need to fly with a local pilot because off the rules.
The oaci designator of Iguazu is SARI and the designator from San Fernando, Bs As is SADF
The distance is aprox 1050 Km
You can get a C210 for 0.85 Us Dolars x Km
or a PA23 radar equiped for 1,10/1,15 dolars x Km
Here are some flight schools web site so you can have a reference and email them
http://www.aerodot.com.ar/alquileres.htm http://www.delta-plane.com.ar/
if you want more info give me your email so I can answer any question you need. I will be a pleasure