Mandarin Chinese, Malay, Tamil, and English all coexist in Singapore as official languages, a demonstration of the melting pot the country represents.
English is fine!
Singapore was a British posession for many years. And unlike India, for example, whose huge size made it difficult to consistently enforce English as a common language, in city-state Singapore it was widely accepted. As a result, the English of local residents is excellent, and you'll have no problem communicating with them, even the ones who are native Malay or Mandarin speakers.