Yep. Post office here is right next door. Road in front of post office is also used as the queue for picking up kids from school. In fact, it's not uncommon for parents to be blocking the entrance and exit to the Post Office parking lot.
So needless to say, it's an area swarming with parents at times who may or may not be overprotective and have the ability to exercise a bit of common sense.
Now, if you visit the post office between 7:30AM and 8:30AM and 2:30PM and 3:30PM, you're in a bit of a conundrum. Do you break federal law with minimal risk and go on and park in the Post Office parking lot? Do you risk a ticket for impeding the flow of the school children pick-up/drop-off queue? Or do you walk 2 blocks from the nearest public parking (or 1 block from a private lot where no one will really report you)? How important is that Post Office visit?
How is it breaking Fed law if you park and leave your weapon in the car outside the P.O.? On school grounds, yes, state law, but it sounds like the parking lot isn't school property. You just can't carry into the post office.