AFAICT you're required to have the chains available, so they're usually in the trunk, unless you're in a situation where they're required. Of course if you buy chains you should immediately put them on your vehicle, if only to ensure that later, when you need them, they will fit. Once you've done that, then you can put them in the trunk.
I disagree with your interpretation of the law: dot.ca.gov simply state what they require and say nothing about which is superior. And note that 4WD/FWD vehicles _also_ must carry chains in the R2 & R3 areas (from the URL you posted http://www.dot.ca.gov/hq/roadinfo/chcontrl.htm):
"(NOTE: Four wheel/all wheel drive vehicles must carry traction devices in chain control areas.)"
Unfortunately for an AWD/4WD vehicle, following this provision costs twice as much as for a FWD car and will take twice the time to install (not an insignificant factor in freezing rain) and, should you fail to install on both front and rear properly, or should they suffer mechanical failure, may put one in a bad situation.
The cost of chains is negligible compared to the cost of the car. The advantage of not having to get out of your car in the snow and put on chains at a chain control checkpoint is huge though.
I disagree with your interpretation of the law: dot.ca.gov simply state what they require and say nothing about which is superior. And note that 4WD/FWD vehicles _also_ must carry chains in the R2 & R3 areas (from the URL you posted http://www.dot.ca.gov/hq/roadinfo/chcontrl.htm):
"(NOTE: Four wheel/all wheel drive vehicles must carry traction devices in chain control areas.)"
Unfortunately for an AWD/4WD vehicle, following this provision costs twice as much as for a FWD car and will take twice the time to install (not an insignificant factor in freezing rain) and, should you fail to install on both front and rear properly, or should they suffer mechanical failure, may put one in a bad situation.
Sometimes it's better to do less.