Argentina in December - Mixed Questions

Howdy all,

Making my first trip down to South America and flying in/out of Argentina December 15th-January 4th. I've done Europe repeatedly and Central America in the past.

I'm 25, social, will be traveling solo and am a hostel/backpacker. Will be budget oriented and trying to keep my total expenses AFTER airfare there/back at 1,5000-2,000 max.

The goal is to see as much as I can while not killing myself or spending the entire trip in a Bus.

Current plan is to be back in BA on the 29th or 30s and then spend the 31st, 1st, 2nd, 3rd and 4th in the city. Will probably spend the first 2 days there as well - 16th/17th.

So, with about 13 days to poke around what can I manage? As I understand it it's about 25 hours by Bus to get up to the Falls from BA? What does that ticket usually run?

Are there any budget/regional airlines that would let me fly south or west to the Andes or given my time frame is that more or less impossible?

Must see things/places?

Suggested hostels?

Ideal itinerary (while keeping it fairly open)?

What other info should I know that I'm not asking?

Thanks all!