One of the reasons the drive-in is so much fun is nostalgia. Going is sort of like sifting through the bins at a thrift store and fishing out an Eisenhower-era night on the town instead of a lamp. The folks at the Boulevard Drive-In know this, so they play it up. The old neon sign near the theater's entrance doesn't appear to have changed since 1950, when the place first opened. And instead of that canned, corporate Hollywood rock moviegoers are forced to listen to at the multiplexes, the Boulevard's staff plays premovie music that harks back to the days when cars had fins and hundreds of drive-ins lit up the national horizon. They play songs by all the old crooners as well as novelty numbers like "My Car Goes Beep, Beep, Beep." They've even dug up a few corny old radio commercials to run between the tunes.