If you get the earliest tee time - I think it's 6am - you can get finished in 4 hours. That gives you 4+ hours to get to the airport, return the rental, and get through security. Be careful not to get behind even a small tourney at RC for they usually take 5+ hours.
Do not underestimate LA traffic. In any other world 50 miles should not take more than an hour particularly after the morning commute. But due to neverending construction, inevitable accidents and inane carpool lanes you cannot predict an accurate ETA for LAX. Be sure to take the 118 East to the 405 South for the quickest route.
Security can also be a nightmare. Depending on the terminal, it can be an hour plus...
LA - we love it!