Whatever you do with it, you're going to have to grow it one town at a time. It'll start in your own, then the next town over, then the next town over, similar to how you described your goals. Unless the new people referred to the site see activity of other nearby people using the site, there's no social proof that it's worth their time to share anything, and there's no chance that something shared will pique their interest enough to give the site more than a passing look before leaving.