Boston wasn't in your list of cities so I lost interest pretty quickly. That's fine, but it looks like there were other cities on your site that are completely devoid of posts. I can immediately think of two options here to improve the experience:

1) Explicitly state on your site that you're only launching in one (or a few) cities, and then actually restrict postings to those cities. You will then probably need to do lots of creative marketing for your site in those cities to get initial traction. You could also have a sign-up form for people who want to express interest in posting in a different city, and then you can notify them when you open the site up to their area.

2) Find a way to easily (and legally?) populate your site with data from competing sites like Craigslist. This way you don't have giant empty sections on the site.

There might be other options as well, but having cities with literally no posts in them doesn't seem to me like it will attract (or retain) users.