Do Not come to CA with any 'assault pistols' - That's essentially any pistol with a detachable magazine and a threaded barrel. All non-'assault pistols' are legal for import.
Do Not bring into CA any 'large capacity ammunition feeding device' - That's no magazine which hold greater then 10 rounds. The only common exception to this is if you possessed them within CA prior to 1/1/2000. It is legal to import magazine parts. So, if you disassemble them prior to entering CA you are legal.
Generally speaking the guaranteed method for legally transporting a handgun in a vehicle in CA is to transport the handgun 'unloaded in a secure locked container' it is legal to have magazines within the same container, but 'loaded magazines' must NOT be within the firearm.
"secure" is not defined, however it is common use in CA to use both soft and hard cases. For example a 'gun rug' with the zipper/s locked. Glove Boxes and Utility Compartments of a car do not qualify as an appropriate container. A locked trunk is acceptable as an appropriate container - however, it is highly recommend that if you use the trunk, its still best to use an additional locked container (you don't want to open the trunk in a hotel parking lot and get popped for an illegally concealed handgun in a vehicle)
In CA it is legal to have a concealed (or open), loaded (or unloaded), firearm at hand for self defense within your residence. This includes temporary residences suchas your hotel room or campsite. Note that this is explicitly your room or campsite; not the rest of the hotel, not on the walk to the group bathroom at your campsite.
CA Penal Code (searchable) is available here: http://leginfo.legislature.ca.gov/fa...Selected.xhtml
In Particular I would recommend searching key words from above within PART 6. CONTROL OF DEADLY WEAPONS [16000 - 34370]
Have safe trip!