Wow - my experience at the same twilight tour was totally different. My friends and I got there a little late (closer to 6pm), and got our tickets at the door. Even though it was crowded, and the parking lot did look very full, people working in the lots efficiently found a spot for us - I feel like I've had worse experiences at places like Disneyland or the LA County fair. (plus parking was free!)
We were able to see a lot of the cats up close - and volunteers near the cages were very helpful in explaining why cats were behaving the way they were (ripping up phone books) and what their habits/characteristics were. Some of the animals were more popular than others, so there was a bigger crowd near them, but we kept moving, and were able to see the entire zoo. It was quite incredible seeing the bigger cats from a few feet away - they are humongous. Other people who work at the zoo willingly answered any question the public had about the cats. We watched in amusement as one of the smaller cats tried to catch goldfish in a little pool (it was getting really frustrated after every failed attempt), and another garfield-like cat just sat and stared at the public. The jaguars were absolutely gorgeous.
The zoo is definitely worth checking out - I've only been there during a twilight tour, so I can't say if it would be better or worse at any other time of the year. I went to the zoo to see exotic animals, and I was able to do that. The beautiful surroundings, the clear night sky, and sharing the amazement with other people just as interested in these animals made the experience a lot better.
Yes - it was quite busy, but seriously - we live in So Cal, and this was a special night in the year with great weather. I wasn't aware that tickets were supposed to be limited, but I was glad I was able to get in with my friends after driving almost an hour and a half to get to the zoo.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC