Cliff, CamelBak has an entire line of hydration packs that look very non military. Bright colors, the whole shebang. Check out their website.

The best thing to do if you're concerned with the possibility of terrorist threats is to ask the rest of your group and see if anyone has been to central america before. They can give you a world of information which really helps when considering what to pack <img src="/images/graemlins/smile.gif" alt="" />