It's not likely that your park brake cables have rusted up on a car driven in southern California.
It is far more likely that you have dry caliper slide pins or something else that is not allowing the pad to fully return. You may also have rotor wear such that edges of the pad just never clear the rotor fully.
You need to pull the rear pads off for inspection. With a little luck you may just need to properly lubricate the pins and everywhere the pad backing plate touches the caliper or the rotors machined or both.
