SAN DIEGO — Big changes may be coming this spring for many San Diego restaurants and retail stores, because city officials say they plan to follow through on a long-delayed ban on polystyrene foam food containers, coolers, pool toys and similar products. City officials said the ban, which has been delayed nearly four years by litigation filed by restaurants and foam container companies, will take effect April 1 if the City Council approves it during a hearing scheduled for Nov. 15. Prospects for approval got a boost Thursday when the council’s Environment Committee voted 4-0 in favor of the ba…