Recently I had to get from San Diego International Airport to the Amtrak Train Station. I had no idea how to do it but it was so easy! Here is what you do.
Right outside of baggage claim you can see the stop for the necessary bus. You need to get on the #992 bus which comes every 15 minutes M-F from 5:30am-6:30pm and every 30 minutes from 6:30pm-11:29pm. On Sat/Sun it’s every 30 minutes until 10:59pm at T-1 and 11:02pm at T-2.
Bus #992 costs $2.25 and you must have exact change. For seniors (60+) it’s $1.10. There are NO transfers. There are stops along the way but if you are going to Amtrak you get off at America Plaza Trolley. The bus stop below is the one you catch the #992 bus.
On the way to the station you get some pretty cool views. The two pictures below are what I saw from my window. 
There you have it! An easy and cheap way to get from one form or transportation to the other!
