I know this is going to sound fucked up, but I usually go on vacation in random places I have never been before and always look for at least one day to smoke. Mainly out of curiosity to see how weed in other countries are compared to the states.
Well long story short I either look for Crack Heads or Bums, sure you have a chance of getting robbed or setup by one but I haven't yet and it works everytime. I offer them some money, tell them I'll hook them up. They take me to the local drug dealer, and I ask him for some good shit. He either tells me he only sells crack or some bullshit or he has it. Normally if he only sells crack, he still knows people who sell weed. Give the bum or crackhead $5 and the dealer $5-10 depending on the area and I get a nice $20 sack. Sure it adds up, but if you're on vacation and want to smoke and don't know shit about the area it's your best bet.
I don't go up to strangers asking if they know a weed spot, because tourist spots ALWAYS have people looking to rob tourist and the last thing you want to do is scream out I got money and I'm looking for drugs. They'll target you because A) Your a tourist B) You don't know the area and they can lead you into a death trap C) You're looking for a illegal substance and if they rob you, you'll just end up snitching on yourself & D) You'll look lost and confused because you don't speak their language and they can be setting you up while smiling in your face.
Don't ask me why but crack heads and bums have always been more reliable to me because they just want their money or fix.
Also NEVER TRUST A METH HEAD OR COKE HEAD! Period. I live in an area where I can tell who does what drugs because I've seen people doing them since I was super small, I can tell a meth head from a crack head. Crack heads are predictable and slow, meth heads will be nice one second and slash your throat another. Bums are usually nice because they just want to get by on life.
Edit: obviously only take your I.D (Not passport) and enough cash to pay off people, never go with your life savings, credit card, family pictures, passport, etc.