Welcome to JustAnswer.
Legally yes you can make a citizens arrest for any crime committed in your presence. I should warn you though that there are many pitfalls that can happen and many police and prosecutors take a dim view of citizens arrests.
For instance pulling someone out of a car could result in someone getting killed. Also, if one of the three other people you were with decided to take some street justice
out on the thief and punch him a few times, you could be legally responsible for that. Obviously we just saw some of the things that could go wrong in the George Zimmerman trial
If you do decide to try making a citizens arrest, you must use the least amount of force necessary to effed the arrest, notify them that you are making a citizens arrest and for what crime, and deliver them to a police officer immediately. Also, remember that while they are in your custody you are responsible for their safety and welfare. Overall, in most situations I don't think it is worth the risk to you both from a legal and safety perspective.
Here are a couple of the California statutes on citizens arrest and a guide I found online that has some good advice and appears to be consistent with California law: