It's best to get the metro bus.
I did street parking. Didn't seem to be any shortage of spots when I went. There's lots of parking garages nearby If you can't find anything on the street.
I caught the bus to go over there. You can get a a daily bus pass or weekly bus pass in the Union Station. I think parking lots are expensive in the FTB since it is located at downtown LA near Third Street areas.
There's a parking complex across the street.
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