I'm not looking for a job at one of the endless English institutes here. I'd like to volunteer my time/experience as an English teacher. Is there anywhere that offers English classes for free or at a reduced rate that needs volunteers?
I did this once. I just offered my free services to someone on Craigslist. I ended up tutoring a young woman from Brazil, which was great for her because I speak fluent Brazilian Portuguese. It makes it a lot easier to explain some concepts if you can just do it in the language that the individual speaks. Anyway, try Craigslist. The top level of the Burger King at Corrientes/Callao is a really good place to meet! Good luck!