Informal urban infrastructures are a challenging environment for participatory design, both from an organizational and technical perspective. In this paper we reflect on a recent research project involving participatory sensing and design of participatory technologies for informal recycling cooperatives. We collaborated with COOPAMARE, a cooperative in central São Paulo, Brazil, on two goals: to map their spatial organization of waste collection, and to develop software tools for coordinating with clients and planning operations. We discuss how GPS tracking, web-based mapping, and mobile applications allow cooperatives to collect, manage, and interpret spatial data themselves, and to redesign their own system collaboratively with others. We argue for applying participatory design in international development projects, which often neglect design aspects, and discuss the social, economic and technical contexts that impact design.