There are lots of cute new babies that you can see
There is a baby giraffe, baby hippo, baby takin (near polar bears). I lied, I suppose, when I told you the only line is for the bus. The OTHER line in the park is for the pandas, so go to see them early! There is a baby (about two years old, but he's still small), and the area has to be kept quiet, so there is a line to get into the exhibit as they monitor how many people can see them at a time. The line can be 30 minutes or longer if you go on a busy, busy weekend, so try to do them first. The pandas are at the bottom of the zoo, so a lot of people reach them in the afternoon, so maybe you can run down there, see them, then head back up to see other things and you'll beat the crowds. Be sure to check out Elephant Odyssey, a multi-million dollar exhibit that opened in May 2009, and Polar Bear Plunge, which was upgraded last spring.
I work in the animal training department. I used to do the big bird show that they had from May 2009 to Sept 2010, then I worked at Backstage Pass (a special animal interaction program), and now I am back to training birds and other small/medium mammals for an interactive show on the front plaza. Unfortunately the show will still be in the production phases while you're visiting or else I'd tell you to check it out!