It was actually filmed in a few places: The diner was in Downingtown, the theater and I believe some of the houses (like the doctor's office) were in Phoenixville. Other locations were around the area and on sets. But the diner (as far as I know) no longer exists. When the theater reopened several years back, they showed the film on the anniversary of its release as a fundraiser/reunion of some of the extras, and it became an annual event.