I live in Indianapolis myself but it's still pretty worthless. I'm sure there's some kids walking around but I'm not where kids are, I don't go to school and walking around everywhere with my 3ds is pretty impractical seeing as I don't have time to play if I'm out doing adult person things. Because that's how most American adults feel, I think.
Streetpass was definitely invented in mind with Japanese society. Many more people there carry their 3DS with them and from what I understand, you can easily find scores of people playing with them on their commute in trains to and from work...or even after work together at social gatherings at various restaurants and bars.
That's not really the case here in America unfortunately. I imagine the streetpass functionality in Japan on the 3DS would work much better here in the US if Apple incorporated a similar feature in their products.
Still, its a neat feature and it's always cool to see it pop up on your 3DS when you do come in close proximity with someone else who has their 3DS on them.