At some point (age is one of them), just getting on a cruise is the fun. Don't need to get off at any port. I'm reaching that point that getting on in San Pedro is more appealing than flying to a foreign county to do a cruise.
OP has lots of options. If they want to do Alaska, ships sail from San Francisco AND Los Angeles. I don't know if Holland or Celebrity do anything out of San Diego.
OP has restrictions. One requires a scooter. Not sure how portable his/her is. Need to get in on a plane and then into a vehicle. Those are huge challenges.
I won't park my car outside (I have a closed garage). I can't imagine leaving my car in a parking structure for many days. This is no different than taking a cruise from New York, or Florida, or....