Budget friendly places in South America

Okay, I’ll keep this as concise as possible because I really need some advice.

I caught the travel bug on my first trip last year and since then I’ve visited more than five countries, usually staying for a while. I’m not exactly rich, so I’ve had to come back to my home base in Canada a few times. Right now I’m getting ready to leave again after working and saving over $5,000 CAD, and I also receive a $1,000 CAD monthly pension.

I’m stuck choosing my next destination between Mexico (Cancún or Mexico City), Colombia (Cartagena or Medellín, where I’ve already been), and Brazil, which would be new for me.

I’ve got a soft spot for Brazil, especially Rio, since everyone seems to be talking about it lately. The only thing holding me back is the cost. Flights are fairly expensive (even one-way), and accommodation over the medium term doesn’t seem cheap either.

I don’t travel like a typical tourist. I prefer staying longer, exploring, and really getting into the local culture. With a budget of around $800 CAD per month including accommodation and utilities, where would you recommend I go ? South America preferably :)