(your inbox is full I can't PM you)
Yes security is pretty lax, especially most of the office towers that are built by real estate corporations. Pretty much like what those Russians did at the ST.
Rain is gonna be annoying. Lightning/thunder/typhoon definitely cancels any trip to the hills or rooftops haha. The other major problem is smog, today was smoggy, the original picture was very gray toned, I had to turn up the saturation like mad in photoshop just to get those colours.
Trekking hills is fine. But since you are a foreigner that do not understand any Chinese, these *rooftop* attempts may not be best for you. If you are really really interested in doing one, I can explain the fine details if you want.