Outside the area, the signal that allows calls to be made and received usually come through another provider's network. The usage fees charged between networks are passed on to the phone user. For cell phones, local calling areas are usually much larger than those of traditional phone lines. For most providers, the Bay Area calling area extends as far south as Bakersfield. Off-peak hours are usually the evening and overnight hours.
Hours vary by provider and individual plans.
Plans usually come with a limited number of peak minutes and far more off-peak minutes than you'll really need in a month. Unused minutes rarely roll over into the next month. Do yourself a favor and sign up for some sort of off-peak or night and weekend plan. You'll save your anytime minutes for the peak hours and can talk freely during the off-peak. If you plan on spending 500 minutes a month on the phone, don't sign up for a plan with an allotment of 200 minutes.