that age thing is really going to hold you back. especially in the states. while banquet halls are cool, the overhead on renting is pretty high. plus you have to rent your own security, insurance, and bring your own PA/Lights. I've done my fair share and its alot more work than you think it is.
here are some suggestions;
talk to local book stores / record stores/skateboard shops and try to make some kind of event or fundraiser. those places love it when new people cruz into there places, and if its for a good cause, win win for everybody.
House partys. especially if you live near a college town. I am sure you know somebody that will let you party at there place, just bring the beer and the people will come.
but in all seriousness once you hit the 21 mark it gets a lot easier to get shows. just keep practicing and make your band really hard to follow.
good luck