You're not too young to go to AWA...people dress up babies and take them! Just don't go by yourself. While the majority of the people there are good-hearted people, you never know who else will be there. Try to get your mom or another adult to take you, just to be safe.
I don't think you're too young, but you definitely need adult supervision. Have a parent or other trusted adult accompany you. I agree with MissUnderstood, better to be safe than sorry.
I been to cosplay conventions twice. I went when I was nine and ten years old. Now, I belive you are older than me, so our not too young! My sister on;y had one friend go with her. Also, it may be more fun without your friends. Trust me, your never too young!