I was just reminded of a walk I recently took in San Francisco's Presidio. There was an art event going on around the Fort Winfield Scott area; exhibits scattered around outside. You could approach this as art. Or you could approach it as a sort of hunt. I didn't approach it as a hunt, but I'm sure it can be done: As I walked around, I saw this young kid run up to one of the signposts marking the way to one of the exhibits, point at it and say "I found a clue!" Yeah, sounds familiar, right?
The event's called Habitats and it's going on until mid-May 2011. I didn't check out the whole thing myself—I was just passing through doing something else. But I bumped into some of the exhibits along the way. I liked one of them plenty; I thought one of them was a good idea with not-so-good execution... Uhm, yeah. If you're an art snob, it might not be worth your time. But if you're looking for fun somehwere at the intersection of art and romping around the presidio and looking for stuff, you could do worse.
Oh yeah, if you are kind of an art snob and in the neighborhood of the Presidio before Dec 19 2010, you could do worse than check out the Fiber Dimensions exhibit, too. They don't make you hunt down the art or anything. But it's kind of neat to see, like, a kimono made out of old coffee filters or textilish stuff even weirder than that.