[villagetinker]

OP, with regard to the lamp post light being on a night, I believe that these are required to be on, community standards would be able to tell you.
I completely agree with using LED lamps. Also, depending on how the house is wired, there may not be a dedicated breaker for the post lamp, ours is tapped off the garage GFI circuit on a box in the attic, labeled 'post lamp', same for at least one of our neighbors.
If you are asking about the switch to do repair work on the lamp, look for a breaker labeled 'post lamp or garage GFI/post lamp' and open it, then double check the ciruit is dead before working on it. Several local hardware stores carry the light activated switches.