I'll be in this same situtation in a year or two. I plan on having the surgery in Bangkok, and then holing up somewhere for a while as I recover. I have both a knee and shoulder surgey coming, and I know I can be diving within a few months after the knee surgery, but am not sure how long the shoulder will take. As SteveB said, and I have heard, shoulders take a while to recover. That said, I was diving 2 days after having seperated my shoulder a few years ago, and I actually found that once I got my wetsuit on, the pressure from the suit and cool water actually made my shoulder feel much better.
As far as where to stay, Bali might be a good choice, as you can get decent diving there and not be too far from decent medical care, should you need it. There is also a orthopedic clinic in Phuket, that I've been looking at as a possible recovery location, but that is more due to the fact that I know Phuket very well.