Introductory physics for life sciences (IPLS) courses have emerged as a type of physics course within the introductory courses sequence. The interdisciplinary aspects of these courses as well as the diverse student populations that they serve create significant challenges for instructors who choose to design and deliver them. The Living Physics Portal is a collaborative project, funded by the National Science Foundation, that is designed to support instructors involved in teaching IPLS courses. As part of the project, a survey was administered to document current pedagogical beliefs and practices in teaching IPLS courses. On this survey, 383 instructors (out of 762 respondents) reported that they had taught an IPLS course in the past two years. We analyzed instructor perceptions about the effectiveness of their IPLS courses in engaging students and examined predictors of differences in their perceived course effectiveness. Descriptive statistics showed that there is considerable variability in instructors' perceptions of the degree to which their courses are effective in engaging students. Hierarchical linear regression analyses identified self-reported teaching strategies as independent predictors of perceived course effectiveness, even after controlling for prior teaching experience and community of practice self-perceptions. We present our results and discuss implications for the IPLS community.