We loved going here. Really cool to see a museum where all of the fossils are collected from the surrounding areas. They are still actively excavating and you can go into the park and see where they are doing their work. The museum is a perfect size. You learn a lot, but don't have to spend the whole day. 1 to 2 hours is great. They have a quick film about the tar pits, and its fossils, which is worth seeing.
I also liked learning about the history of the museum. The modern history of the tar pits and museum goes hand in hand with the history of L.A. Very informative.
The museum is right next door to the LACMA and there are food trucks right across the street. Makes for a fun day in L.A.