Unless you had the magazines in California prior to the ban, you can't bring them in. You need some 10-round magazines to be legal.
Check out http://californiaopencarry.org for a bunch of PDF files with a ton of information on the various minutia which we have to deal with to stay legal. The big ones are to stay out of public buildings (post offices, police stations, city halls, etc.), stay 1000' away from K-12 school property (or lock it in a fully enclosed locked container), and keep it unloaded with your loaded magazine in plain sight unless you are in unincorporated territory.