If I were to try it. I'd let them come to me and ask for whatever and then pop the question.
Then say here is all I have and only have what your willing to give out in your wallet, for them to see that its empty when you open it up and hand it over.
Stay on the outskirts of several not to get in the middle and take a friend. Older cloths, unshaven and bad hair would help.
Even go hang around without a camera, talk some first.