Violence erupted over the weekend between striking workers and guards at one of several struck wineries in Northern California, as talks were about to resume in the harvest-time labor dispute. Bronco Winery representatives accused picketing union members of throwing rocks at grape-filled trucks near the company's plant south of Modesto, while union spokesmen accused company guards of harassing union members. A temporary restraining order was obtained limiting the number of pickets at the winery. A hearing on a permanent injunction was set for today. Negotiations, which have been stalled since the strike began Aug. 18, are expected to resume today in the dispute involving the Winery Employers Assn. and two locals of the Winery, Distillery and Allied Workers Union, representing about 700 workers. The strike centers on several money and maintenance-of-contract issues. In addition to Bronco, the struck wineries are Christian Brothers, Franzia, Vie-Del and Lamont.