We do have a Yelp Account and we have 4 reviews. We also have a coupon offer on Yelp but have not received any interest so far from that. I can't say that it has helped us much at all. I notice that the studios that have paid ads tend to have a lot more reviews so perhaps that is the key to Yelp, pay them for advertising to show up in the searches. We come up 22nd on the list of yoga places in Oceanside, which doesn't make any sense since yoga studios in other cities come up on the list before us. I believe that is probably connected to not paying for an ad.
I have also tried a Groupon coupon and we did find a couple great students that have stayed with us. My experience with Groupon as well as Living Social is the majority of users are really looking for a discounted price and a lot of them go from studio to studio, using up the coupons but don't stay for long. It is good exposure, however, I think it makes it harder for the client to transition to paying the full price for yoga classes. I have found it's better to offer my own special discount on classes rather than such a deeply discounted price.