BERKELEY - Several thousand UC Berkeley graduates and their families flocked to the university's Hearst Greek Theatre for Wednesday's commencement convocation, only to have their graduation speaker leave campus rather than cross a picket line. California Assembly Speaker Fabian Nunez, D-Los Angeles, declined to speak while 15 to 20 members of the union representing University of California service workers demonstrated outside the theater to protest low wages for UC custodians. "The speaker doesn't cross picket lines," said Nunez spokesman Richard Stapler. UC Chancellor Robert Birgeneau stepped up as the substitute speaker. Leaders of the American Federation of State, County and...