An irony of the coronavirus pandemic is that the idyllic beach vacation in Mexico in the brochures really does exist now: The white sand beaches are sparkling çlean and empty on the Caribbean coast, the water is clear on the Pacific coast and the waters around the resort of Los Cabos are teeming with fish after 10 weeks with no boats going out. There are two-for-one deals and very eager staff. It’s all only an airline flight — and a taxi ride, an…