They are getting interest through their traction in other cities. Since they are already in 20 cities and have approximately half a million users if you look at their Android app (https://play.google.com/store/apps/details?id=co.hinge.mobile.android), they can simply wait until one city "tips". ...
Well, you'll certainly have a lot of options for where to focus your marketing efforts, since entrepreneurs are a huge market and pretty much everywhere on the web. I'd recommend testing some different social media channels - grow a brand presence on the major networks, and if you have the budge...
To build on what Sarah said - you can also look within channel if you have access to someone with the technical chops. Some ad groups or campaigns could be driving "worst" leads and others could be driving "best" ones. To cut off the channel is throwing the baby out with the bathwater. UTM tag...