I second the opinion that driving, or going by bus, should not be an option. If you're to adventure in South America, drive in Pantanal, currently these are the months to be there as there aren't floods. Poor roads but magnificent scenario with wild life and magnificent birds.

For information regarding Foz de Iguassu, you can either go there from the Argentinian or Brazilian side, though the view is much better from the Brazilian side. Recently I've posted some information that I suggest you give a read at Inexpensive carriers in Brazil . Just note that in that post prices have been informed in AUD - Australlian Dollars. Give a 15% disc over those prices and you'll have them on USD (US Dollars).

If you've additional questions, feel free to ask.

Enjoy your time around.