Are motocross bikes and ATVs street legal?

I live in Sacramento, California. I have a dirtbike like they use in motocross. Can I ride it on the road or sidewalk? By the way I'm 14 and don't have a drivers permit. I would like to know if I could use it for transport. Also can I do the same with my atv? I have the permit to own it and all that legal ****. I just want to know if I can use it in the city anywhere and what are the rules. Thanks in advance.