From our experience this spring, on disembarking in San Diego after the WBPC, I can tell you that there is a
DCL sponsored bus from the port to the airport. I would assume (but do not know this to be true) those same buses would then take the next group of cruisers from the airport to the port.
I can also tell you that if you have some time to kill, it's totally not worth $35 per person. We did it because it was our first experience in San Diego. Next time we will take a cab and save a bundle.