My 2 cents...I think 2 nights in IGUAZZU FALLS with 1/2 day in Brazil (if not too far over your budget)is so very well worth it. Staying in the Sheraton adds a visual pleasure and the convenience of being right there - and able to return to change/rest after the more moist adventures. YOu may want to take a taxi to town for dinner.

We preferred to stay in the town, as we were interested in the cultural aspects, but it is truly a matter of preference and budget. Missions are said to be good for visiting too.

Take insect repellant and sunscreen and enjoy yourselves.

Producerkoof: The ride between the 2 airports shouldn't take longer than an hour. However, if it's a week day it may take a little bit more due to traffic. The fastest way to do this is to take a taxi or have a transfer arranged.
In case you need further information, here is a link to a forum regarding this topic: http://www.fodors.com/community/sout...n-airports.cfm

I hope this helps! Enjoy our country!