I would suggest that web design services is going to have a very low conversion on Yelp. One of the best ways to advertise design is through Dribble, Behance and sites like it. Generally speaking, unless you've got a compelling offer that you attach to your campaign (e.g. free consultation), you're likely going to have pretty low conversions from typical ad networks, to the point where I don't think it would be worth the money.

Happy to brainstorm some more creative ways to rise above the noise.