I agree with Rotch, definitely Patagonia. Also while you are in Buenos Aires, try to get to Tigre, you can take a boat tour, and it's a really relaxing way to spend a half a day. I also suggest that you make sure that you eat a parilla in Argentina, they are amazing restaurants that have the best meat you will ever eat in my opinion.
As with all travels, I am agreeing with Cyberia, just be careful with your valuables. It doesn't mean you have to be extreme about it, but have some common sense and be aware of where you are, and what is going on around you.
If you are going to the Falls in Argentina, try and get to the Brazil side, too. Both sides are worth at least one day of exploring, and the sites are amazing!! Buses will be the cheapest way to get around usually, although definitely not the fastest... Some times, just the amount of time you can save by taking a plane will make up for the cost of it! You may want to, as Cyberia said, look into the local travel agencies, they can make it way easier, and usually cheaper to get from one place to another. Have fun and safe travels!!
Im planning to do pretty much the same route as you are, although i'll be starting in Peru. It is quite a place
Check out southofhere.org. It's a pretty cool site about Patagonia. The entire Chilean coastline is incredibly beautiful.
Throughout South America, they have ATM machines everywhere to withdraw money, but just be aware that the ATMs will run out of money. I got stranded in Pucon for 3 days because I couldn't withdraw money to pay for the rest of my stay at the hostel. They were cool with it, but it was a headache for me.
-snip- I'm still in Santiago, Chile I picked up work as an English Teacher. It's very easy to do, and people are always willing to pay straight cash. This city is awesome, but expensive.
Good luck and have a blast.
[ Edit: Sorry, no promos please. ]
I am also planning a similar route to sully. I have only decided recently however and have not finalised my travel plans but will be arriving before the end of Oct hoping to finish up in Rio for the middle of Feb. Up until now I was planning on starting in Lima but sully has got me thinking about colombia and ecuador. Would you recommend spending some time in these countries? Has anybody done a home stay to pickup some more spanish on arrival Any information would be great
I would definitely reccomend Colombia. Spent around 1 month there at the start of the year as part of a larger South America trip and it was possibly my favourite country. The place is incredible. Didn't spend a lot of time in Ecuador but heard very good things from other people.