Of all the local Chinese operas, I think Cantonese Opera is probably one of the most active and visible ones. Apart from the professional opera groups, there are a number of amateur ones and many are taking an interests in it.
Inside Chinatown, the Kong Chao Wui Kun (Gang Zhou Hui Guan 岡州会馆) , Gang Zhou Association, which is probably older than its building which was built in 1924, is offering Cantonese Opera Singing lessons 粤曲教唱班. This Association has been amongst the pioneers in having a Cantonese Opera and a Lion and Dragon Dance troupe.
So, if you are interested in the singing class, call them at 62239806. The building is along New Bridge Road, opposite to Pearl Centre.