Sandy Dillon

THERE was something sleazy about the basic idea of ''Beatlemania'' - four ersatz moptops reducing the Beatles legacy to a plastic simulacrum. But the multiple-screen projections and other special effects that were created for the show by its authors, Bob Gill and Robert Rabinowitz, were genuinely fresh and appealing. It was only a matter of time

FOLK ART Among the places that catch the discerning vacationer's eye out where the sidewalks end are those that display those weathervanes and samplers, old signs and quilts, the things designated folk art, relics of less fevered American years. Actually, one doesn't have to go to the country to find an impressive showing of folk art. For 20 years