In my experience, a good thing. Community theatres are places where just about anyone can go equipped with 32 bars from Godspell and be in a real-life, honest-to-goodness play.
Got a little acting bug inside you that's buzzing to get out? Check your area for community theatres and see a play or two at each of them. Find out which ones do quality work, then find out when they hold auditions. Pick a theatre you think you'd like to work at, a show that sounds interesting, and give it a shot.
If it's a musical, you will have to sing. Singing is not nearly as hard as people will lead you to believe. Nine times out of ten, if you can carry a tune in a chorus, you're in.
You may have to dance as well, but don't panic - if you miss every step, but smile, and are in a group of dancers hitting every step perfectly but not smiling, you will appear to be the only one getting it right. Don't let them know you have no idea what you're doing.
Above all, have fun. This is not Broadway. I've seen some much-too-determined folks at community theatre auditions. Relax!
If you don't get in, try again some other time. Most theatres do four or five shows a year. If you do get in, great! Keep a positive attitude, show up for rehearsals on time and ready to work, and directors will love you. Even if you're not the most talented person in the cast, a director will remember you if you're easy to work with, and will very likely cast you again given the opportunity.
Community theatre is a great way to have some fun creating real, vibrant art. You'll impress your family, make new friends, and have lots of funny pictures to look at later in life.