Hey at least Manhattan has bike lanes now and there's a huge cycling push in new york city, and you are right hong kong island is really dangerous to be in a bike, most people will think you are crazy. And if you are crazy, just ride like you stole it to keep up.

this might help:

http://www.mapmyride.com/hk/hong-kong/

but notice none of the trails are really in hong kong island but in lantau island which is nice and far away from the main city. Looking at where you are you might have to take a train to get there from fanling. Also what bjorke said there are bike trails around the new territories so you can scope that area out too, someone who's from HK here might be able to help you. Also since you are a folding bike enthusiast they do have group rides monthly:

http://www.youtube.com/watch?v=PxeeWKEpU38&noredirect=1

You might want to contact the poster of that video if you want to know more about their folder club. It's a start else I wouldn't know where to direct you to since I live on the other side of the world.