Probably, for a photo-shoot. Definitely, for a convention.
I know you're supposed to cosplay for yourself and not for other people, but please consider your own safety. Not everyone at a convention is a good person, and there are a lot of true horror stories out there. Also, if you meet a genuinely nice person and you happen to look... well, *good* in your costume, it could make the other person quite uncomfortable when they learn that you are underage.
RIP CosRevo, Love Laugh, Sweety Pop, Cocosilver.