SAN ANTONIO—Gay rights victories in Texas haven’t come at the Capitol but at city hall. While nondiscrimination bills in the Legislature languish, Houston has a lesbian mayor and Austin offers health benefits for same-sex couples. But in San Antonio, conservatives are pushing back against one proposed stride—an ordinance that’s virtually identical to measures adopted in every other major Texas city. The San Antonio City Council is expected to vote today on amending its nondiscrimination code to include protections for sexual orientation and gender identity. The local issue has drawn top-line Republican opposition from such heavyweights as U.S. Sen. Ted Cruz...