入乡随俗 - in idiom, is 'when in Rome, do as the Romans do', which is sometimes shortened to just 'when in Rome', or 'do as the Romans do'. 'If we go to China, we are going to do as the Romans do, and learn to use chop sticks. 水土不服 - not acclimatised (British spelling). I have been in Singapore for three weeks, and I am still not acclimatised.