While the autonomous nature of free-choice learning can have numerous positive effects on student learning in science fields, there is a lack of research on how college-age adults learn in informal settings. The purpose of this study was to quantitatively describe college-age adults' experiences at informal learning settings by administering the Informal Learning Experiences Survey (ILES), which is intended to serve as a tool for practitioners to reflect on undergraduates' participation in learning experiences at informal settings. We administered the ILES to 441 introductory biology undergraduates in Fall 2018 at a single institution and found the most commonly visited informal learning setting in the last six months among our participants was city, state, and national parks. Further, participants reported that their main reason for learning about science at informal settings was for fun and enjoyment, and that their primary barrier against engaging in learning at informal settings was limited finances. We hope the ILES will (a) allow instructors of introductory college biology courses to reflect on and describe the prior experiences and interests of their students related to learning in informal settings, and (b) inform program directors at informal learning settings about how to better incorporate experiences designed for college-age adults.