We stayed at AKL last summer (jambo house) and when we were at the bus stop by 8:10 we were at the parks by 8:40 at the latest. I think the actual ride time is about 18-20 minutes, it just depends on how long you wait for a bus. If you want to be there for the opening show, I'd say be at the bus stop about an hour before opening and you should be fine.