Sure. There is no restriction on taking your own firearms out of state and bringing them back. Of course, if you took out a firearm that should have been registered in Ca. as an assault weapon, you wouldn't be able to bring it back (not that you weren't already in a problem situation if you had it unregistered at home).
You can transport registered assault weapons out and back as long as they are transported in compliance with the laws on transporting assault weapons.
Note that legally removing the AW from the state is one of the approved methods of disposal, or if inherited, desiring to transfer, etc.
https://oag.ca.gov/firearms/regagunfaqs#8
I'm pretty sure one generally can only be a legal resident in one place at a time, that governs federal and state purchase laws, CCWs, etc. If "moving" into Ca., there are registration requirements for new residents, can't import AWs, etc. IIRC, the idea that you can take and leave firearms on out of state property that you own (perhaps rental is OK as well) is covered by federal law, too, like you can't leave them with another person (on their property) without dealing with time limtis, transfers, etc.