San Cristobal is a beautiful town, and a great place to learn spanish. I would however recommend you have at least a rudimentary knowledge of the language, because outside of the tourist-centre, no one speaks a word of english.

I survived with just a phrase book, but there were times when I just couldn't make myself understood. AND I stayed in a hotel in the centre. So either bring a very big phrase-book and prepare to make a fool of yourself, or learn some basics and the rest will come to you while you're over there.

Either way, I'm sure you'll love it.