Have a read of this.
http://www.hrpu.co.uk/karennben/notes.html
I met up with Karen and Ben when they were in Australia and they done some serious kms through south america.
If you have a read on the lonely planets forum you will also find more info on riding in South america.
It looks good and I wish you well. Your from Buenos Aires and I'm sure you'll be ok but I don't like being robbed though and it seems that nearly everyone who cycles there is. Lots of places in Europe and Asia to cycle.