Truth is most will only make it to some basic Cantonese phrases with a hard accent and it will help only as an ice-breaker. But point is putonghua or commi speak won't bring you any further with the locals and different to Cantonese won't even help as an ice-breaker. Again, English is one of the official languages, so for anything related to the job or with the authorities must be in English anyways (if in doubt the English version of a contract, letter etc. prevails) and everybody can speak some English, except for some retarded Chimomms tourists/immigrants.