The de-facto official dialect of Hong Kong is Cantonese, a Chinese dialect originating from the Guangdong province, spoken by 90% of the population as a first language. Mandarin, the official language of the People's Republic of China, is also becoming increasingly common and may even one day overtake Cantonese as the main language of Hong Kong.
Although English is widely used in government bodies, the business community and in most shops and restaurants in the business district, the degree of proficiency is limited in the more local or smaller establishments. While many non-locals feel intimidated by Cantonese, it is possible to learn some basic words and phrases to converse with people on the street. People are usually pleased that you are trying to learn the language and will generally be encouraging and helpful.
If you plan to be in Hong Kong for quite a while, it is the worth the effort to enroll in a course to learn to speak some simple Cantonese. You will enjoy your time in Hong Kong far more if you are able to converse with the locals in their own language, as well as making yourself more attractive to employers. The language is quite hard to learn as it incorporates 6 different tones, which means that one word can have six different meanings depending upon how you pronounce it. However, if you persist you will slowly begin to get a good grasp of the vocabulary.
A basic course in Cantonese typically runs between two and three months, and focuses on oral skills and listening comprehension. Courses are centered around useful vocabulary, daily expressions and sentence structure to help students communicate in a range of everyday situations.
There are a number of reputable language schools offering part-time and full-time courses, as well as private and group lessons geared towards foreigners and expatriates. Course fees range from HK$2,300-HK$5,850 depending on the size of the class, and usually include books and teaching materials.