Well I wonder if in big states like Montana, with one calling area, if all calls in the state are local? :Q
Anyways, since you are in So Cal (IIRC) if the number of the phone has the same area code as the number you are calling from, it should be a local call (as sated by the Pittsburgh/Miami post earlier)
It is the cell phone user who will get the extra charges if they are 'roaming' or out of their 'home coverage' area.