Zoological Society of San Diego

Less crowded than the Main Zoo at Balboa Park and lot more open space. Unlimited Tram Rides. Parking is $ 12, ($ 9 for members or free for Diamond Membership) We get the Dual Diamond Membership for $ 140 which includes free parking here and unlimited visits to the main Zoo and the Wild animal park for me and my wife.
Tip: Come here early on the weekends because it is much cooler and less crowded. Also get on the Tram before 11:30 to avoid long lines. Some of the exhibits to see are the Tiger Trail, Lion exhibit and Gorilla exhibit. You can get real close (Just a thick piece of Glass between you and the Animal) and see how they interact. I have seen the Lions Male and Females fight over a Large Leg Bone the trainer threw out — It was Really cool.
Also check out the Cheetah Run usually once a day at 3:30. 0 – 60 in about 3.5 seconds. Really amazing to watch!