Every major car manufacturer and leading technology company today is pursuing the development of Connected and Autonomous Vehicles (CAVs). However, given cities will be most affected by CAVs, there is an urgent need to assess whether our cities are prepared and will respond well to the advancement in CAV technology. This paper proposes the first readiness index to measure the extent to which current cities are ready for CAVs. We consider three key elements in computing a CAV readiness score: a city's policies and regulations, its physical infrastructure, and its cyber infrastructure. We identify 16 major factors related to the key elements contributing to a city's readiness, and compute the readiness index as a weighted average of these factors. Moreover, we collected survey responses regarding the importance of each factor from 13 of the most populous US cities. We also selected a metric for quantifying each factor, and collected the corresponding data from our survey and existing studies. We then leverage decision trees as a machine learning model to predict 52 major US cities' readiness for CAVs. While it is difficult to draw general conclusions on our cities' readiness due to limited data availability, our preliminary study does suggest that there is a big gap between our industry and public's interest in CAVs and the policy and infrastructure support provided by our cities. Most importantly, we believe that the proposed readiness index provides practical guidelines for policy makers and planners to improve their cities' policies and infrastructure to facilitate CAVs.