Cache idea - Share your Thoughts

Okay, so I'm working on a new cache idea. I have a deck of flash cards that each is a map and fact sheet about the U.S. states and territories. One card per state or territory. And, I'm going to try to pick up a small world map somewhere, probably a fold-up one, because I haven't found country flash cards. The idea is to make this a small cache that people come to and mark on it where they are from. I was thinking maybe that all people would put a dot on the map where they are from if it isn't marked yet, sign a log, and if they are the first person from a state, they get to sign the state card, too. So the cache would have a goal: to get all the state cards signed, and as many dots from all over on the map as possible. I'd probably sign the Colorado card myself and take a picture of it to put on the website and show folks what they're supposed to do. I need to find a good, secure hiding place that isn't too hard to reach. So I'm open to ideas on working out the kinks, etc.