The San Diego Zoo is a regular outing for us. The one time admission tickets are quite expensive, but the season passes are quite reasonable if you plan to go often and come with a magazine and coupons.
My favorite part about the zoo is not only seeing animals (obviously) but walking through the beautiful grounds. The plants and vegetation are truly beautiful. The zoo is also hilly so it is a good workout for me strolling along with the kids. I love to walk around in there.
On the downside are those awful tour buses. At several points in the zoo the pedestrians and the buses share the road, and this is not a good situation during the summer, where there seems to be one coming by every couple minutes. They are also very noisy and terribly smelly with the exhaust fumes in the area. Therefore, I definitely avoid the zoo during peak times because of those tour buses. Winter weekdays are really ideal times for the walkers and nature lovers.
I find the food is not good at all so we usually bring a lunch. The food there is not horrible but it on the whole is not very healthy and quite pricey.
The Skyfari is worth it at least once for the view.