Well, it's very easy! Go up to somebody that looks like they smoke. Ask "hey you know where I can get some trees?" If they smoke they will know what your talking about. Simple as that.
It is not hard to find marijuana if you go to the right places. Places such as skate parks, chill hang out spots, beaches, and of course college campuses. There are many more places you could go but, these are the most common places you can get some bud on your vacation.