Sammy himself gives a rather accurate description of the location of the A&P store in his town. Note the following quote that comes from his account of what happened on this day:
What he meant was, our town is five miles from a beach, with a big summer colony out on the Point, but we're right in the middle of town, and the women generally put on a shirt or shorts or something before they get out of the car into the street... if you stand at our front doors you can see two banks and the Congregational church and the newspaper store and trhee real-estate offices and about twenty-seven old freeloaders tearing up Central Street because the sewer broke again.
The A&P store therefore seems to be located in the centre of a normal middle-class town that lies next to the beach. The way in which everybody is so shocked by the girls who come in with their bathing suits on indicates that middle-class values such as decency and modesty are very important, and that the community is shaped and driven by this values. This is why of course Lengel challenges the girls and tells them not to enter the A&P again in this way. In addition, you might like to think of the way that Sammy refers to the people that use the supermarket as "houseslaves" and "sheep." This clearly presents the community as being traditional.
One of the striking features of "A&P" is that Updike is describing things that everybody is familiar with. This makes it easier for the reader to visualize the scene and the event. Everybody knows what supermarkets look like, and how the patrons look pushing their shopping carts around and waiting in line to pay for their purchases. Everybody knows how apathetic the checkers look and how officious the managers act. Everybody has seen skinny, self-conscious, but pretty young adolescent girls in bathing suits. Updike is making use of what his readers already know. Andy Rooney once said something like this: My greatest pleasure as a writer is to tell people what they already know but didn't know they knew. A good writer is observant. He doesn't just look for extraordinary things, or beautiful things, but is especially aware of the ordinary things. "A&P" is a famous story, often anthologized, just because of its ordinariness. After all, it is just about a minor flurry in a small town caused by a young girl in a bathing suit who wants to purhase a single grocery item.