Get out your mop-top wigs: Today is Beatles Day in San Francisco, and a large crowd is expected to gather in Union Square to sing "All You Need Is Love," say reports. It was in the City by the Bay that the Fab Four gave its last public concert, in 1966, and it is the San Francisco-based publisher Chronicle Books that is publishing the $60, 370-page Beatles autobiography, "The Beatles Anthology," today. Excerpts were published in British papers last month, and among the revelations was George Harrison's tale of the group's meeting Elvis Presley and his Memphis Mafia in Hollywood in 1964. "I spent most of the party trying to suss out from his gang if anybody had any reefers," recalls George. "But they were 'uppers and whisky' people. They weren't really into reefer-smoking in the South."