This is THE worst spot we've been to in Southern California. It's overcrowded, and while that's an issue at many places, the staff is untrained in handling crowds. Be ready to have yourself and your kids pushed around, stepped on, and held up in one spot because there's no one there to keep the crowd moving out of the walkways/paths. The preschool/toddler (up to age 5) play area has no staff monitoring - there were kids up to 12 years old in there climbing on top of the equipment and jumping off. My kids, 2 and 4, got hit by a 3-year old who was also hitting other children while dad "asked" him to stop. Whenever one of the younger kids got to play with something, an older child would jump in and take it over. Yes, kids do this stuff, but there is no one around to keep things in order, and who wants to fight with the other parents?
Be ready to have your kids wait in long lines to just see a small, simple exhibit. Be ready for kids, as well as adults, cutting lines in front of you with no one to stop them. Be ready to watch adults hogging exhibits meant for children while children wait for minutes and minutes on end. Try explaining this chaos to your small child. Why he/she can't see anything, and why after waiting their turn like asked, someone just jumps right in front of them and they have to wait even more.
Besides all that, we've been to Science/Children's Museums in many other cities, and this place is a pathetic example. The exhibits are a big jumble. The exhibits crowd each other, not just the people. And though they've tried to have themes going in each area, the stream doesn't make sense. The only real exhibit is the bat exhibit, the rest is just a bunch of themes thrown together.
This place isn't a museum, it's a human zoo. I consider the $30 we spent a huge waste. If there's anything to learn in there, you can't learn it because you won't get to see it. Take your family somewhere else, anywhere else!