Just to be clear, CA Penal Code 626.9 prohibits possessing a handgun
within 1,000 feet of any place accredited in teaching any grade K-12. However, this only applies if you know, or reasonably should know you are near a school. (Since you're visiting, it might be harder to convince the jury you should have known there was a school two blocks over.) Further, you can exempt yourself from 626.9 by securing your handgun within a fully-enclosed, locked container.
My recommendation is that you keep the pistol in a belt holster while driving. If you have to stop for any reason or if you discover yourself entering a "gun free school zone", just lock it (and the ammo) in your gun case on the seat next to you. When you're back on the road, take it back out.
I do NOT recommend dash-board or seat-top open carry, since a sudden turn or bump in the road could cause your handgun or mag to slide off and end up under the seat, leading to a violation of concealed carry laws. (Court precedent holds that a full mag being concealed can be a violation of CA PC 12025.)