I'm working on Agrobiodiversity fairs in the Colombian Amazon, like a strategy to empower local communities and strengthen their traditional knowledge.
Organizing Agro-biodiversity fairs in rural communities is the only means to empower rural world. Such fairs would also attract urban communities to visit rural areas to purchase the products which are cost effective and affordable. Whereas, city based mega shopping complexes such as Walmart, IKEA, Costco etc are constrained to hike the product prices making them customer unfriendly and unaffordable, as they have to levy transport, storage costs on the consumer public.
There are many experiences in Mexico, most of those that I am aware of are in relation to maize, but I am sure they must also include probably many other genetic resources related to the milpa. You should try contacting Flavio Aragón (INIFAP), and Amado Ramírez (Itanoni), these are some of the people who have had experienes with these fairs and could guide you. There is also an exprience from the federal government trying to finance such fairs (again, mostly tied to maize) in CONANP (the program is called PROMAC), you could contact Juan José Arreola and also Elleli Huerta from CONABIO. My personal opinion is that fairs are key in providing means as for correctly valuinging genetic resources in local and regional contexts, incentivating seed exchange among communities, among other things. It results as a tool in strenghthening "the process" by which agrobiodiversity evolves.