This is a very niche site. I would think that the type of people that would be into this service would be (mostly) over the age of 35. What type of marketing/market research have you done for your target demographic? Do you have an advertising campaign set up to reach your target?

You have to realize that the kind of people that would like to share restaurant experiences are probably not the same type of people who enjoy discovering the latest web 2.0 website just because it has been launched two weeks ago.