People think that the Mexican-Riviera cruises are nice and warm. Well..... it is nice and hot in Mexico where you can wear shorts and tops, sandals.
BUT....leaving from Los Angeles.... the weather can be real cold so you need to also pack warm clothes like jeans, sweathers, and warm jackets for walking around the cruiseship until we get to Mexico.
The Ocean in Mexico is always cold no matter what month it is so be prepared to swim in cold water. But the sun will be out and it will keep you warm.
So pack summer and winter clothes for the Mexican-Riviera cruises.
San Diego port can be really cold too in the evenings. You need a warm jacket to walk around by 6 p.m. in the Fall. Winter is a given that it will be either cold or warm.... we never know.