Hostel Inn is very good for a budget place. Avoid Foz do Iguacu as much as possible - it's a charmless midsized Brazilian city, much dodgier than Puerto Iguazu. The Argentine side of the falls is also much better, although the panorama from the Brazilian side is worth an hour or two. If you are from the States, you don't need a Brazil visa for day trips across the border - local transport doesn't stop at the border post anyway unless you ask. Ciudad del Este, in Paraguay, is worth a peek, if you're into enormous contraband markets. You can walk across the Ponte da Amizade from Foz, and be back in Argentina by dusk.
Don't know about buses, as I was coming from Curitiba.
