Food in large cities is one of the central issues on the agenda of food sustainability. Various organizations, both official and non-governmental are promoting agroecological transition and alternative food networks. To success, small local producers have to be able to access to these organizations, which requires social and cultural capital. In this paper, we present the results of a research carried out with little production units in the conservation land areas of Mexico City. In particular, we analyze the social relationships that allow them to insert themselves in the networks and make their productive projects economically possible. The heads of 60 households were interviewed and a typology was constructed according to objectives and scopes, origin, types of land tenure, relationships with government and NGO agents, marketing strategies and construction of narratives on sustainability. The results show that social and cultural capital is fundamental for the economic viability of the agroecological transition of small production units, where trust and reciprocity are fundamental. The producers have different trajectories, origin (some are new rural), age and schooling, that are important to determine social and cultural capital. This diversity is an expression of complexity of rurality in contemporary societies, in particular in mega-cities from global south. Our results provide elements for the discussion on the new ruralities in the framework of the global environmental agenda. It also shows that public policies for a sustainable food system should consider the socio-cultural characteristics of the populations.