The Teachers Infusing Technology in Urban Schools project (TITUS) at the University of Illinois at Chicago is developing an approach for addressing the shortage of opportunities for teacher candidates to experience technology being used effectively in high-need urban schools in the course of their field experiences. Beyond recruiting mentor teachers who are already adept at teaching with technology, our work has involved developing communities of experienced teachers within urban schools--prospective mentors for preservice candidates--whom we support in learning to teach with technology. In our first year of intensive work with these groups of potential mentors, we have found a number of assumptions and patterns of interaction that can present problems for infusing technology, and we have explored a number of strategies for addressing them. These challenges often involve a trade-off between different approaches to professional development. Some of these challenges are presented in the paper, followed by examples of how we have addressed them in our project.