Plans to build a new $350 million liquid natural gas terminal in Baja California were unveiled yesterday by the El Paso Corporation, but a Mexican city is withholding approval due to environmental and social concerns. The Rosarito municipal government has denied El Paso a land-use permit, and the city’s mayor has described the project as good for the corporation but bad for people. El Paso is just one of several natural gas companies that would like to build terminals in Baja, because of its proximity to energy-thirsty California and a perception that construction permits are easier to obtain south of the border.