Other than housing costs (and if you have a paid-off home by the point of retirement, you have that problem basically licked) what makes San Diego particularly expensive? OK, gasoline is about 25% more expensive than in the rest of the country, but you’re not paying for energy in other ways, since HVAC costs are minimal.
Food and other goods didn’t strike me as being horribly expensive in SD. Yeah, you have state income tax and sales tax, but it’s not huge in the grand scheme of things.