Yes the only law that really limits the ability to freely travel with an unloaded firearm in California is the state version of the "Gun-Free School Zone Act".
Because of this and only this law it is recommended you transport in a locked container.
The legislation does nothing to protect children from those intent on harm. Yet manages to control most of the state's population having nothing to do with schools because they will need to travel within 1,000 feet of a school on roads.
So it is one of those ingenious anti-gun maneuvers which on the surface appears to apply to just schools or 'protecting children' while applying to virtually every member of society going about their daily lives.
Who wants to be the politician arguing for the repeal of legislation titled "Gun-Free School Zone Act"?
Are they against children?!
Scenario: A short trip to the mall, best buy, In-N-Out burger, Starbucks etc... Am I legally allowed to open carry so long as I am not within 1000 feet of a school. These are not government buildings or sensitive areas, such as an airport or courthouse. I may keep a 1911 on my hip, unloaded, and magazine pouch(s) on the other hip so long as both are fully visible.
Officially? Maybe.
However the people that do these things in cities for demonstrations and to alert people of their rights normally set it up with the police in advance by alerting them to the event beforehand. The police then often show up to monitor the exercise. Since they cannot ever cross a school zone they won't be going too far from the initial location. Confined by the borders of school zones.
The same action by a regular person without alerting the locals in advance is eventually going to result in tense interactions with police.
It may not happen the first time. You may even get away with it for a week. But make no mistake you will end up confronted by police with drawn weapons in most of the state. You may have a resulting legal battle.
To remain officially legal you will need to research the location of every single school near you, and stay more than 1,000 feet away. Stay even further away just to be sure. 1,000 feet is greater than the width of most roads, about the length of 3 football fields. This means your little outing will probably be impossible without extensive research. Certainly not just casually going where the mood takes you.
Here is one of many resources for locating the address of every single public or private school that you must stay 1,000 feet or more away from:
http://www.cde.ca.gov/re/sd/
Newer schools may not be immediately on such a list.