how long have you guys been dating? really there isn't anything you CAN do short of calling the cops and busting them. and i'm pretty sure if you did that there would be hell to pay from several people. if it bothers you then don't hang around there. and if he hates it like he says he does then he probably doesn't want to be there either. and he's not the one doing it so it really shouldn't be something to end your relationship over. if you really want it to last then you need to find a way around it. ending a relationship over someone else's actions isn't a very good strategy.

whenever i'm in a situation like that i try to think of WHY it bothers me. I can't control others' actions so why would I let it bother me? I think you need to get to the root of why you're so uncomfortable around something that's pretty common and accepted just about everywhere. and is becoming more and more legal. pot isn't something you can avoid and will eventually be legal in the u.s. so you should probably learn how to get over being uncomfortable around that drug because it's virtually everywhere and will be legal before you know it.