Another tip if you're renting a car - 2 out of 3 times I've rented a car for a road trip in Argentina, I ended up cracking the windshield (rocks thrown up by a car or truck). It ended up costing me about US $150 each time - much cheaper than it would have in the US. If you have an option to get some kind of insurance that would cover this (ask specifically about the windshield), I'd probably get it.