it depends on which Kaiser region you're in, how busy they are, and how often they hold orientation classes. You should just call the Bariatrics department and ask.
Personally, I was already scheduled for orientation before I had my initial psych interview, so there's really no answer to your question, unfortunately. For me it was only about 3 weeks between my Overview and Orientation, and I had my surgery about 3 months after Orientation which I was told is very fast.