California does allow suction cup mounts but only in two specific (generally unhandy) places...
http://www.dmv.ca.gov/pubs/vctop/d12/vc26708.htm
says that in regard to something blocking the driver's view...
(12) A portable Global Positioning System (GPS), which may be mounted in a seven-inch square in the lower corner of the windshield farthest removed from the driver or in a five-inch square in the lower corner of the windshield nearest to the driver and outside of an airbag deployment zone, if the system is used only for door-to-door navigation while the motor vehicle is being operated.
If you take advantage of this consider having a printed hard copy of the law as some law enforcement officials are not fully aware of this. I've been stopped once and fortunately could cite the vehicle code provision.