I know that you posted a long time ago and this advice won't help you as you've gone on your trip already, but I do have some advice so I thought I would post it anyways in case someone else has the same question!
The Center for Disease Control's website is awesome, it tells you which vaccines you need for each area: http://www.cdc.gov/travel/vaccinat.htm
I needed vaccinations because I'm also going to South America, and I went to Passport Health to get them. It costs about $50 for the consultation and the vaccinations are costly but I couldn't get them anywhere else. I did try and get any that I could from my physician though, like Hepatitis A and my tb, things like that. Also, for things like malaria pills or other prescritions I went through my pharmacy rather than paying the passport health price ($10 copay vs. $8 a pill for malaria, and for malaria I needed 17 pills). If you don't have health insurance you might just have to pay the high price though.
Here's a link to passport health: http://www.passporthealthusa.com/locations/index.html
they give you a nice vaccination form to go with your passport with official stamps and records of your vaccines so that you can have proof of them. If you don't have a passport health clinic in your area I'm sure there will be some type of travel clinic close by (hopefully!) Even though I ended up spending around $300 for vaccines from the clinic I do think it was worth it. They give you a lot of information on the areas that you are specifically travelling to and tell you about the diseases that you may encounter and symptoms, what they are, etc.