In order to ask the question, the cops have to have a "reasonable suspicion" that a crime has occurred. Five guys drinking coffee does NOT fulfill that requirement, 911 call or no 911 call. There have already been plenty of cases in the category of "driving while black" where the limits of seeking evidence for secondary offenses lie.
I’m not an officer, so I guess it’s a judgement call. Maybe some freepers that are, could tell us how they would have responded?