I attended Mike Dowling's Greater Yellowstone Music Camp several years (wish it was still happening). You couldn't have asked for a better setup/environment. It's been a while, but will try to highlight to the best of my recollection.
The camp was held at a ski resort during off-season. The setting was beautiful, and the accommodations were perfect--there was a big lodge, with nice rooms, plus a huge lodge room for gathering and jamming, There were also rooms to accommodate the instructors/classes, of varying size, as well as some outdoor areas set up. Since it was a resort they had a small store, and more importantly a big bar on site--another place to gather an jam. There were also activities for non-musicians like my wife, who loved it for hiking, riding the ski lift, horseback riding, and so on. They had a kitchen staff and all meals were included--so really no reason to leave the site for the whole week.
Yes, the camp should have a "focus" and this one was all about Blues and Swing. They had known instructors for the different genres, which I think is a big part of the draw. They ran 4 classes per day, and you could sign up for the ones you wanted--descriptions were given in the program with regard to levels, but I think you could still participate in the sessions you wanted to. Each night one (or group of instructors) would perform in the bar (which had a stage and sound system). On the last night the "campers" could sign up to perform a song, either solo, or with an ensemble that you assembled.
Everything was "all-inclusive", so you didn't have to worry about reaching for your wallet the whole week, and it made for a much better experience. I believe there were options to "room share" to help with costs, and you might have been able to eliminate the meals and lodging if you wanted to stay at a motel in the nearby town and pack your own food (but I'm not sure, and I don't think anyone did this). Lots of good friends were made, and I still mourn the ending of the camp, as does my wife.
Of course this is on a pretty large scale, but I can't imagine a better setup. On the other end of the spectrum a smaller scale weekend, or even a "workshop" for a day are options--I've done "day" workshops with a morning and afternoon session, and an evening "house concert" with the instructor, which was also fun (and a lot cheaper). Good luck!
Some pics from GYMC back in the day:
Me with The Teewinot Jug Stompers (my group that I assembled for performance)
Me performing another year:
Some friends jamming in the lodge:
Bar shenanigans!
Me and Orville Johnson--one of my instructors that week:
The wife loved the camp as much as I did!
