Thanks for the suggestion. There are a couple ways to do that:
1) you visit the member list, and browse by location... http://www.happycow.net/members/members_list.php?sortby=location&sortmethod=asc
2) You can type a location in the search box at the bottom of the member's list page. However, it will also include results of members who have listed favorites and reviews in that city as well.
In the near future we'll be working to improve the search feature.