Don't promote BitCoin on the grounds that their value is rising and it's a good investment. That's
a) Risky. What if the value of the currency falls? People will blame BitCoin when they should blame you.
b) Unhelpful for BitCoin as it takes coins out of circulation. The point of a currency is to circulate.
c) Makes BitCoin seem about frothy speculation instead of trade. We want the BitCoin brand to be associated with legitimate, beneficial economic activity, not currency speculation (which is the domain of investment banks and thus has a very poor reputation).
It's probably way too early to be promoting BitCoin on the streets, though your intentions are good. If you did want to do this, you'd be better off with a street stall that sold goods for both national currency and (at a discount) BitCoins. People would be motivated by the discounts to investigate BitCoin.
Of course, we'd need to solve the in person trading problem first, eg, with mobile phones. We didn't do that yet.