Book a flight between LAX and San Diego International Airport, SAN, to get from one city to the other by air. Flights take approximately 45 minutes, but if you include the time needed to navigate airports, flying may not be much faster than going by land.
Take the train between the Los Angeles Union Station and the San Diego Marina for a public transportation option that's as easy as flying but is much less expensive. Travel time via Amtrak is around three hours.
Rent a car or drive your own to get from one city to the other on Interstate 5, I-5. Travel time on I-5 is about two hours, depending on traffic. Much of the drive offers scenic ocean views. If you have extra time, you can visit hotspots like Anaheim, Laguna Beach and La Jolla along the way.