How do you say no to people like that.
Very simple… you tell them no. If it’s illegal in your jurisdiction, you can tell them that too. If you have a cell phone, you can offer to call them a cab.
I suspect that more often then not they’re just poor innocent people(Chassidish or Yeshiva Bochurim) looking for a bit of extra help.
You’re right, probably the vast majority are fine, upstanding people. So, by all means offer them help. Give them money for the bus, offer to call them a cab, etc. But don’t let them in your car unless you know who they are. The risks are, IMHO, just too great.
The Wolf