We actually did two hopscotches, one smaller and more normal and an epic one with triangles, path choices and 44 different "blocks". I am working on getting a slide show up on the blog of all the pictures I got, but until then:
A couple things that need working on: having a small child hand out bottles of bubbles is great, but small child will need to be older than three or have a little more prep time or be hugely extroverted. Thinking out a path that is meant to be used might catch people's attention more (use of arrows and "this way" type things). Strangely, actually talking to people about it seems to work. They might not have time to chat for long, or play, but the interaction was all positive this time and because the chalk will last for a few days, I think some of them will wander back by and try things while no one is looking. Human self-consciousness was definitely an issue.
The people chalking and observing had more fun with it than people passively encountering the instructions, but hopefully this will inspire more random acts of whimsy and positivity in different forms.