The National Girls 18 and Under Championship is being played this week at the Berkeley Tennis Club and the Claremont Hotel, next door.  256 entrants, plus parents, syblings, friends, coaches and college recruiters.  Fifteen or twenty courts in progress; free admission; and good seats at all venues.  All races, religions, and nationalities (counting the parents) represented, and not one serve-and-volleyer at work.  Future touring pros and college number ones and (many) never-to-be-heard-froms.  Saw no racquets thrown and heard only one expletive uttered.  It was the round of 32 today, with the quarters tomorrow.  Pick up a sandwich at Rick & Ann's, a coffee at Peet's, both across Domingo St., and spend a some enjoyable hours in the sun.