Always a great time. Sunscreen and a hat are a mus...

Always a great time. Sunscreen and a hat are a must. You can bring your own food and drink. That's a good thing because NOTHING is cheap. If you are locals spend a little bit more and get the yearly pass, it works at the safari park also.
One day is not enough to see all that the San Diego Zoo has to offer. Make a weekend or a couple of days out of it, at the least.
The bus guided tours are a great way to let your feet rest and see the park from a different perspective.
I personally recommend the California Condor exhibit. Somebody's always hanging around that works there and is willing to tell you all about it, they have a very fascinating story.