Thanks to all who contributed to this thread. Super helpful to see what others have been through.
My story, and what i learned
High level
AC separation, grade 2 or grade 3 depending on how you look at it. In either case, surgery is not necessary, and I opted not to have it. The more I read, the more happy I am about not opting for surgery. Recovery time (measured as being able to ride again legitimately): 13 weeks.
Here's a bunch of detail
Measuring whether it was a grade 2 or grade 3
The traditional way is to look at the distance from the tip of the clavicle (where the AC, or acromioclavicular ligament sits) and the acromion on an x-ray. The more reliable way, according to my ortho, is to measure from the middle (not the tip) of the clavicle to the coracoid process, where the trapezoid / conoid ligaments sit. If that distance is between 110-160% of what it should be (using the other shoulder as a comparison), then it's a grade 3 ... you know you have a good ortho if they spend the time trying to figure this out ... also, I am going off of memory here, so I might've gotten the ranges slightly wrong.
Implications of grade 2 or grade 3
No surgery for grade 2. Grade 3 is a grey area. The majority of orthos that I spoke to cite the same research when it comes to deciding whether to have surgery or not. The research followed hockey players, who have a high incidence of AC sep, crashing into barriers and such. They found that for grade 3, the prognosis is the same whether you have surgery or not. The ortho will likely say something like "you can choose between a bump (the clavicle sticking out a bit) or a scar (from the surgery)". It seems like a rationale reason for the surgery is if you care about how you shoulder look (e.g. you are a young lady). For me, I didn't see any benefit and a lot of downside: pain (apparently shoulder surgeries are quite uncomfortable to recover from), longer recovery time, and risk of infection etc... . So no surgery for me.
Recovery process
The day of, it hurt like a *****, and having no concept of AC separations, I was really worried that it was the end of my riding, tennis, golf and everything else days. I had a minor concussion, felt nausea, heart was racing, I was sweating like a dog ... I calmed down when they stuck me with morphine at the hospital. I was surprised at how much strength i still had in my arm when they tested it various ways at various angles. They sent me home that night, which I was also surprised with as I thought I would be admitted for some sort of surgery. Interesting side note ... every single medical professional I met had had an AC sep (ER nurse, ER doctor, Ortho Nurse, Ortho Doctor, Physio). I guess that's how they roll in San Diego!
Week 1: I took the prescription painkillers for the entire week, and stayed home the first 2 days, though was able to work (conference calls, writing one handed emails etc...). I took a lot of naps, and could sleep ok, but not great, on my good side. The pain was dull and constant, and I wasn't able to do much of anything with my shoulder. I also had flesh wounds, which my wife helped me with. Generally I was using 1 hand for most if not all of my activities. My wife drove me around, I had to sit in the backseat on the side where I could put the seatbelt over the good shoulder. Whenever the car went over a bump, I could really feel the instability in my shoulder ... it was quite uncomfortable. I also had to wear a sling. It caused pain on the other shoulder, partly from carrying the weight of the arm. It was all a big pain in the ass.
Week 2: Still wearing a sling. Switched from the prescription painkillers to over the counter, though had to go back on a couple of occasions because I needed the pain to go away. I was back at work every day, and still being driven. I could do a little typing on the computer with the bad hand, but it got tired quickly. I used voice recognition software a lot, which is not as much of a time saver as I thought.
Weeks 3-4: Ditched the sling, started driving myself around. tried to cut down on OTC meds ... generally succeeded ... started physio. once I found a PT I liked (the difference between an average and good PT is shocking), i was very aggressive ... twice a day, 15-20mins min per session. Most of the exercises were trying to get the neck and shoulder muscles to relax (they freeze after trauma, for protection). Still in some occasional pain, limited arm movement, couldn't lift my arm above my head, couldn't shave with that hand, had to wear button down shirts so I didn't have to bend my shoulder into a t-shirt. Generally was getting worried that recovery was going to take forever, given the incredibly slow pace of improvement.
Week 5: saw a step change improvement the day after being in the pool for an hour or so. Shoulder and neck muscles seemed more relaxed, and was able to do quite a bit more. Arm still got tired easily. At work, I always looked for ways to rest my arm on something (arm rest, table).
Week 6-8: gradual improvements, but no step changes as observed in week 5. Continued aggressive PT ... could raise arm above my head by walking fingers up a wall. Now back typing on a computer, almost normally, though was getting tired easily. Taking occasional OTC pain killers. Can only sleep on good side or on back. Still couldn't use my arm to shave my head, because of awkward reaching back motion.
Week 9-12: Rapid progress being made over these weeks. Was finally able to put my hands behind my head. Able to put on a t-shirt without screaming. I could hold planks legitimately (more of a week 11-12 thing), ventured out on the bike week 11, though on the road. Lifting the front tire to get on/off the sidewalk was a little painful, but manageable. Arm tired easily, and I took painkillers after the ride.
Week 13: Did my first legit mountain bike ride. Still a little soreness at the tip of the clavicle, but good amount of strength. I walked the bike on harder segments ... no point in taking risks this early. Confidence is certainly lower than before, but I expect it will come back as I put the miles on. Had to take pain meds the next day.
Week 14: Did a bunch of riding, and it all felt solid. I am also swinging a racket, and hitting a ball with good strength. Taking pain meds the next day about 50% of the time after physical activity. Wished I had done some exercising throughout this ordeal as I lost a lot of fitness (I've seen others say the same thing), but it's coming back. Graduated from PT, though I continue the exercises. I just recently was able to shave my head with no discomfort from the awkward reaching. A lot less instability inside the shoulder ... but I still can't sleep on my side, and there's no way that I can do a push up. I heard that takes 6 months to 1 year.
In closing
I hope this helps others set expectations on how the recovery goes. For me, it was definitely a story of no noticeable change / no noticeable change / no noticeable change / big change / no noticeable change and so on.
One of the important aspects seems to get those muscles to relax ... I tried massage and that was very helpful ... being in the pool also helped, so recommend all that. Be patient with the recovery, do the PT and try to get some exercise in.
Good luck and see you on the trails soon!
Note: I had to go off memory for a bunch of this stuff, so consider this directional, and thanks in advance for any corrections (primarily on the medical explanations!)