The Zoo is basically two hills with a canyon in between.
Yes, you can take the Skyfari one way - either take it from the entrance area to Polar Bear Plunge, or from Polar Bear Plunge back. There's not much to see on the Polar Bear Plunge side ride now - except for Polar Bear Plunge. They are doing a big construction project (Elephant Mesa), so the area that used to have most of the antelopes, gazelles, giraffes, etc. is closed, and from Polar Bear Plunge all you can do is either take the Skyfari back, or walk down into the canyon past the raptors (which I happen to find interesting). That takes you down to the bottom of the canyon, where if you walk another 200 yards you'll get to the panda exhibit. If you don't want to walk back uphill (either up Cat Canyon or Bear Canyon) then not too far from there is an escalator that you can take most of the way to the top of the canyon to Gorilla Tropics, though you'll still have a little bit of uphill walking to get back to the Zoo's entrance area. Lots of monkey exhibits to see on the way, though - Gorilla Tropics, Absolutely Apes, and Monkey Trails and Forest Tales.
I'm not sure about taking your stroller on the Skyfari - there's not a lot of room in the cars, so I think most strollers would crowd you. If you're planning on doing a round trip it might be better to just leave the stroller at the main Skyfari station.
I would recommend the bus tour because you do get to see a lot of the Zoo, and learn about the animals, and then you can decide which areas you want to go visit on foot. If you want to see the pandas or koalas up close you really have to do that on foot. Also, you will not see any of the monkey/ape/gorilla areas from the bus.
Hope that helps.
