Your mileage may vary! There was one lady here who was back at school and work three days post-op! That's just a wee bit extreme, though. I was out two weeks during our semester break and then did half-days for another two. I'm a professor, so it's definitely not a desk job!! It was tiring, but not painful or life-threatening.
If you don't want to tell folks all the gory details but you are asked where you were, you can always say that you had abdominal surgery and you'd rather not go into the details. In their minds, abdominal surgery = cancer

or something similar

. They'll respect that. If you never lie about it, you don't have to worry about keeping your stories straight, but you are under no obligation to tell the whole truth, either!!
I didn't tell anyone but my wife about the surgery, probably for about the same reasons as you. After I hit goal, I was open about it and would bend anyone's ear who would fake interest!! Fifteen months later, when my wife had her RNY, she told the world all about it through the entire process, pre- and post-op. I'd already cleared the path for her, so if anyone tried to tell her horror stories, she'd just point at me and say "that has not been our experience."
Good luck as you prepare!
CT