Go ahead and bring it. You can carry it slung over your shoulder. They will check the rifle at the entrance and make sure its unloaded. They may also put a zip tie and tag through the receiver, so you may not be able to insert a mag.
Do not under any circumstances bring or buy any ammunition for your AK at the gun show. Ammo for other calibers is fine.
http://law.onecle.com/california/penal/12071.4.htmlCode:(g) No person at a gun show or event, other than security personnel or sworn peace officers, shall possess at the same time both a firearm and ammunition that is designed to be fired in the firearm. Vendors having those items at the show for sale or exhibition are exempt from this prohibition.