Failed contract negotiations between union hotel workers and several San Francisco hotels have resulted in work stoppages, two weeks after Unite Here Local 2 voted overwhelmingly to authorize a strike at 31 properties in the city. Last Thursday, union members began a three-day strike at the Grand Hyatt Union Square in San Francisco; they returned to work on Sunday but have called for customers to boycott the hotel. Approximately 350 workers at the Palace Hotel, managed by Starwood Hotels & Resorts, began a three-day work stoppage yesterday, which will continue until Friday morning. At the heart of the standoff is affordable health care and retiree coverage, issues on which the union says it is not willing to concede. Union members have been on the job without a contract since mid-August.