Just as a matter of respect and professionalism, every expat should at least attempt to learn the language (and customs / culture etc) of the country he is working and living in.
I do not profess to be fluent, far from it, but I get by and my local amigos all seem to agree my standard is above average
However, I know some expats who have been here a loooooooot longer than me and still do not speak anything and almost REFUSE to learn it - those old school types, you know the ones. Probably in EP. lol
I am still new, only been here 10 years so far, but most of my day I am surrounded by locals so probably easier to pick up anyway. At least I know when I get in a taxi, it is always "where are you from, how long you been here, so you speak Bahasa, are you married (why not) and did you have your lunch yet"
Plus I always just say "sedikit aja" when asked if I can speak Bahasa - better to pretend to be stupid and listen gleefully as everyone gossips about me thinking I cannot understand!