This a a great zoo with an even better aquarium. We were followed around by peacocks all through the zoo, and managed to get up close and personal with the adorable baby sea otter that was rescued from Alaska earlier this year. The trainer happily answered our many questions and zoo staff members were friendly in general.
We too were disappointed by not seeing the sea dragons in the giant tank up front, as they're really expensive and thus hard to find. However, we asked a staff member and were pointed to a tank on the lefthand side as you start walking through the aquarium, near the rest of the seahorses. So if they're missing from the large tank, look there or ask around!
Staff recommended early to mid-afternoon visits to see panthers/tigers/lions being more active; apparently late morning is prime nap time. Also, for every vantage point you get of an exhibit in the zoo, walk a bit further before you take 50 pictures. There are many spots to view each of the exhibits and they seem to improve as you walk further into the park. This is especially true of the giraffe and ostrich exhibits.
There are a few petting options available--you can mingle among the sheep and goats, or stand on a path within the deer and kangaroo exhibits and hope that they come over. We had better luck with the 'roos than with the deer, oddly enough.
There's a AAA discount available online; no discounts for AAA or students if you buy your tickets at the zoo. Giant Eagle usually does discounted passes over the summer that become available in early June.