This is the most convenient and cheapest way to be telecom connected while you are in Hong Kong if you are a visitor. You can buy the China Mobile cards for only 45 HKD at the 7-Eleven at the airport upon arrival. This will give you unlimited data, wifi at all buses, and wifi at MTR (subway), plus you'll get 10 HKD worth of talk time. The data is a bit slow at 2G but the wifi service is fast.
If you have any problems, go to any China Mobile and the helpful guys will fix it for you. Also, if you run out of minutes, you can top up at any China Mobile location, of which there are many in Hong Kong. They all speak English. Also, there's 24/7 tech support that speaks English on the phone.
Be sure to sign up for the unlimited data immediately or you will be charged for data per minute. This will run down your card to zero in just 2 hours if you have a lot of apps on your phone that require background data. Instructions for doing so are included with your card in English and Chinese. read more