I second this- I think that demonstrating potential, a willingness to learn, and an openness to the experience are things that college interviewers would be looking for. Personally, I would also come in with some ideas about what you would like to learn- I think being able to show your interest in their program and what you can learn there would be something great that you can talk about during an interview. Being able to say, "'I'd like to learn more about musicals," or "I would like to understand more about _______". Definitely a good conversation starter, and this also gives them an opportunity to tell you about their program.
Being able to show your potential is great- you'd be surprised at how other things you do relate to stage management. If you have experience in something else that relates (organization, supervising people at a summer job, sign language, dance or music training, etc), be prepared to talk about it. Use the experience that you have- it might be something that makes you valuable to them in some way.