How long are you going to be in Japan? Metro HQ garage (east of Union Station) is $6 a day. But it could add up if you are in Japan for a long time. So it might be worth your while to take public transport from Long Beach to Union Station and then take Amtrak to SAN instead of driving to Union Station.
On your return, from LAX to Long Beach, you can take the Green line to Blue line. I like this idea better because the "G" shuttle to Green line station runs every 10 minutes so you don't have to wait very long.
But if you want to leave your car at Union Station, FlyAway is pretty straight forward when you come back. The bus will take I-105 and I-110 HOT lane all the way to Downtown LA so it goes pretty fast. The only catch is that the bus only leaves every 30 minutes so depending on your arrival time, it may involve a bit of waiting at LAX curb side.
Last edited by bzcat; Jun 25, 2014 at 5:12 pm