Older couple from California, I would stop and explain the law. Group of young guys, don't even bother, they will one star you for not breaking the law. In general if they are a group, locals, or young they're going to rate you low if you accept and won't let them drink. But there's no hard fast rule, if they seem at all entitled don't bother giving them a chance. I haven't had this occurring as often lately, probably only took one or two drivers canceling on them before they realized that if they wanted a ride they better finish the drinks first.