The "northamerica" file's quotation of the relevant decree mentions "los municipios de Tijuana y Mexicali" but only "la Ciudad de Ensenada" (rather than "el municipio"); we may get to use the largest city in the Ensenada municipality that's south of the city of Ensenada.

That seems to be Rodolfo Sánchez Taboada (Maneadero) (22,957); the normal 14-character limit would suggest using Maneadero;
it seems to have a larger population that San Felipe (16,702). Lázaro Cárdenas (16,294) is substantially farther south and thus likelier to use Mexican rules; some 14-character-limit creativity would be required.

Of course if we were lucky we'd discover that Santa Isabel actually uses Mexican rules.-S