You try.
It's as simple as that. I know so many people that ask that same question. They never try-out, and now they will never march. Don't make that same mistake.
About the time issues with school work, etc... It's all about how you look at it. You have to be passionate with what you are doing. Not just with drum corps, but with everything in life. Everything matters. If you figure out that you have more passion for drum corps, that's great. If it's the other way around, then thats just the way things end up for you.
It may end up that you want to be totally committed to your DCA corps. Anything can happen. It doesn't hurt to try-out.
Good luck,
Tony