The President was at a speaking engagement (fund raiser) and stopped at this party on the way to the airport. Look at the picture below. That looks an awful lot like a residential neighborhood to me-probably not the only/quickest route to the airport from wherever the fund raiser was held.
There would be nothing wrong with actually planning to stop at the birthday party, as I said I like it that he did that. I just don't think that Bush would do something like demand to stop at an event like this without getting the thing signed off on by the SS.
See post #31. I have no doubt that a route through a residential neighborhood was planned (because it would seem unlikely to would-be assassins) but not the stop.