Mike, GA stands for General Aviation. It's all the private flyers and smaller (unscheduled) commercial operators (ie. in HK GA means HKAC and Heliservices near Shek Kong). Everything else is military, government or on schedule.
I come across a company called JetOne which offer ground school in HK and arrange training and exam in LA.
The instructor of that course is the vice president of the HKAC. They've never done it before if I am not wrong. No point in taking that course if you can get the DVDs and books from Amazon or asa2fly.com IMHO... and sooner or later you will have to go to the USA anyway. Ground school is the least of your problems normally. Just check online with many of the student pilot forums and sites what books are recommended and start learning. A PPL is a license to learn anyway.
But again, it all depends WHERE you want to fly. If your aim is to fly in HK only and you have a lot of spare cash and you don't care about anything else, then the HKAC might be a winner for you.