Actually, if you travel a lot then you should have a good observation especially for peoples and you can tell whether he is nice and kind or just goofing around so don't have to tell anything until unless it is very important. Just ask whatever you want to ask and leave the place. Good Luck!!
It depends on several things:-
1)Place (as in city/country) & Time you are travelling to.
2)Area of the city you are in (whether its popular and crowded or secluded).
3)Also if you frequently travel you realise whats good to be told and whats not.