This is what I was told when I was taking the course to obtain my permit. In California, if you do not have a concealed carry weapons (CCW) permit, under no circumstances can a loaded gun be transported in a vehicle. The gun must be unloaded and secured in the trunk or in the rear of the vehicle. It cannot be within reach of anyone in the vehicle. The glove box does not constituted as a secure area. Also, any ammo or loaded magazines must be stored separate from the gun. It would be best to have a locked container for the gun and separate bag for the ammo and magazines.
I was also told to never volunteer that you have a gun in the vehicle, regardless of whether you have or do not have a permit. However, if the officer asks you whether you have a gun in the vehicle you should always answer truthfully and show your permit if you have one.
California has some of the most stringent set of laws concerning the ownership of handguns and guns in general, including the transportation of them. Furthermore, it is extremely difficult to obtain a CCW permit in California.