BAD: We will be touring the famous fruit-growing districts.
GOOD: We will be touring the famous fruit-growing regions.
BAD: The original inhabitants of the district were probably Chinese.
GOOD: The original inhabitants of the region/area were probably Chinese.
district = (1) one of the official divisions of a city or country: 'the London postal district', 'the South Cambridgeshire District', 'the Liverpool 8 district of Merseyside', 'Last winter several London health districts faced a cash crisis.' (2) an area in a city (or sometimes in a country) that has a particular quality or feature: 'a very wealthy district', 'one of the most deprived districts in the inner city', 'an old slum district where the gangs operate'. A region is usually a large area of a country and has no official boundaries: 'The President has declared the region a disaster area.' 'Such expansion would most likely occur in the Amazon region.' 'The people who live in this region have a strong accent.'
When you are unsure about which word to choose, use area . An area can be large or small and has a very general meaning.