I picked up on this website, which provides quite a lot of information on eating in various international cities, from a brief mention in the New York Times travel section:
http://www.culinarybackstreets.com/ The particular service that caught my attention was that, for $100, they prepare a custom suggested eating itinerary in one of the cities they cover. Since we are going to Mexico City, which they cover, I ordered one of the itineraries. They ask a series of questions (survey style; not a telephone conversation) such as where you'll be staying and what kinds of places you like. While we have not been yet done the trip, the end product we received seems quite nice. I'll be happy to have it when we're there. They include all meals, market places, as well as some general information. What particularly impressed me is we'll be going between Christmas and New Years Eve when, as we found out, most of the fine dining restaurants are closed for vacation. Since the fine dining restaurant they recommended was closed, they conducted a search for me, based on what we were interested it, and found one that was open. They also made the reservation there.
I'm sure many people here, as I normally do, enjoy the food research we conduct before going to an international destination. However, given what we're spending on the trip, I was happy to spend the extra $100 for some local advice. I'll report back on how their recommendations work.