A few years ago, before we left, I joined the SD Zoo (membership). In the long run it was cheaper for us, plus I rec'd a few meal discounts, in park transportation passes and even a few free day passes to give away. Also their newsletter, etc.
Worked out great for us, as we went back before the annual membership expired too.

Great parks!
Tip at the SD Zoo. When it opens, go to your left to the Skyfari. Ride over to see the polar bears. You beat the crowds. And when we were there, they were only letting the young (playful) males out in the morning.
Another great zoo membership perk -- the Skyfari was a free ride (unlimited) to members. Non-members had to wait in line and PAY $1.50 each way (and may have been per person).
It's been a few years ago. So it might be different by now.
SD Zoo is a very (steep) hilly park. But between the trams, escalators and Skyfari, you can beat them.

AND by JOINING, the membership is TAX DEDUCTABLE!
