At least in Singapore there is a huge difference between an official language and what people actually speak and understand. Although English is the first official language, many (especially working class) people have a very very limited English level and barely speak a few sentences with terrible pronunciation. This e.g. includes taxi drivers, people working in a hawker center or a supermarket.
Questions like "Excuse me, do you have poultry?" have to be reduced to "Hello. Where chicken?". I was not able to ask for an acid based detergent in a super market because nobody could understand "acid". Often these people only speak their original language (Mandarin or Malay) properly. This is additionally hindered by the strong Singaporean dialect.
Even many educated people have a strong accent, make grammar mistakes often and will fail to understand you, if you speak British or American English. Your conversations will be much more fluent and hassle-free, if you can switch to Mandarin.
Recommendation: If you approach a Chinese looking person, which are the majority of people in Singapore, speak Mandarin.
(Source: I have been living in Singapore for two months)