That might be doable as the airport is so close in SAN, but it's definitely risky....
We have a flight out from San Diego at 7pm after our cruise in October. We are not sure what to do with our bags, but I think we might just rent a car and sightsee a bit more before going to the airport around 5. Or, we may see if the Manchester Grand Hyatt (where we are staying prior to the cruise) will let us store bags until later in the day.