I only have experience copping open air on the East coast, big cities.
New Jersey obviously I would say is #1 in terms of open air markets. There are so many big cities spread out over and they all are flooded with high quality and plenty of heroin and coke. Newark, Jersey City, Elizabeth, Paterson, Irvington and the list goes on. And down south is Camden/Trenton. It's all run mostly professional by straight drug dealers who care about business and customers and won't rip you off. It's easy to find. Just hit the projects and apartment complexes or the more notorious blocks and streets. Just watch your ass for the cops.. aside from patrol there is a narcotics unit, VICE, the DEA, etc all over. But my god it's just too easy. First time I went to Newark by myself with no experience, I drove around an area I heard about, was whistled over quickly. The dude wasn't a dealer, but a junkie and he knew why I was there. I took him to the spot and we both benefited. I got a spot and I threw him some for hooking me up. Quick and easy. JUST WATCH OUT FOR THE COPS!
NYC. People say open air in NYC is dead, and while it is not a zoo like in the 70's, 80's and part of the 90's. It is still there very much. Parts of Brooklyn (Bushwick, Williamsburg, Flatbush, Bed-Stuy, etc) There are project complexes all over. Great place to look. Even people on the street you can have luck with if you have a good read on people and approach them with some confidence. NYC you got to watch out for the cops too, especially TNT but it's safer than Jersey in my opinion. Don't forget the Bronx (tons and tons of drugs there in the open), Harlem still popping a bit, Washington Heights, etc. You just have to know what you are doing a little bit or at least act like it. Have a good eye for people and cops and don't draw attention to yourself. Dealers and junkies always have their eyes peeled. If they feel you are around an area looking for something, they will flag you down.
PA - Living in East PA just over the border from NJ temporarily, I have some experience with PA. Philly is obviously easy as shit. Very easy. It works similar to NJ cities. Just watch for cops, know the areas well and pick your marks. You'll be served in no time. I lived closer to Allentown, PA which is the heroin hub here in the Lehigh Valley. Big Puerto Rican population. But it's a crap shoot. Virtually no open air, although if you ask around the streets enough you can get a line in somewhere and meet a dealer. Takes a little but more networking than Philly or NJ. A lot of the dope is coming from NYC/NJ/Philly/weight, cut and grammed up or bagged in folds themselves. This can be a good or bad thing. Lots of drugs in Allentown, but it's kept underground much more than Newark, etc. If you grew up here, you would have no problem, but just moving to the area I had to do a lot of legwork networking, but it's not too bad. Although I would rather go to, NJ/NYC just for the quality/price and convenience especially if I had a phone dealer.
If anyone wants any tips for copping in open air cities, especially the ones I named, I'd be glad too. I've picked up quite a few over the years.