Well, what we did in Guam was we started out with just one or two of us, and then kinda spread the word about parkour through Myspace, friends, and acquaintances, and now we're up to about 8-10 regular practitioners after about 6 months. If people are a bit confused about what parkour is, try your best to explain it to them, and possibly try to direct them to some of the staple Youtube parkour videos. Try your best to be passionate about it. You'd be surprised how infectious a little fire in your voice can be. Convince them. Some folks really do wanna try it out, but they have those last-minute excuses like, "Ehhhh, maybe I'm a bit too outta shape for it". My big selling point is that I used to be like 60 lbs. heavier when I first started practicing parkour, so that helps me sway those folks. You probably don't have a similar situation, but I'm sure you have something of your own that you can make work for you.
Hope that helps.
Good luck, train safe!