Because you're on your feet, and have no props around (as a street magician), you'll need tricks that you can easily carry around.
NFW is great, and is an example of a
packet trick.
Packet tricks are supplied with just the cards needed for the effects, and they're almost always gaffed cards. They're good on one hand, because you can carry lots of them, as they're quite compact. But, the disadvantage in your situation is that they're quite hard to pass off as anything other than gaffed cards.
Packet tricks which I'd recommend are Ultimonte (in my opinion, the strongest table-less three card monte routine) and NFW (already mentioned by myself and The Master Mog).
Other effects you could look into are things like the McClintock Twist video, which gives you a beautiful and mind-blowing routine with normal cards.
Also, coin magic's quite good. Get some nice shiny American Half-dollars and learn something like Sankey's Messiah Vanish, or some other coin sleights - they're compact, and really do impress.
Any more thoughts will be passed on to you, but going for lunch now
