My husband and I just returned from California.  We started our vacation in San Diego and visited the San Diego Zoo.  I have always wanted to go there and am so happy that we did.  What a great zoo, the animals are in great enclosures with loads of space and great thought out areas.  We found that the zoo itself is very environmentally conscious which is such a great asset.  Walking is the best way to see the zoo and you need to allow a minimum of 5 hours to see it.  We took the Bus first but didn't really see much except the overall zoo itself and how much area it actually encompasses.