It rather depends on what you are doing with the data.
For this sort of thing, a standard is invaluable. Locally, postcodes can be used but internationally things are different. You may have countries with smaller populations than some cities in some provinces in other countries, so dividing provinces and cities is not always appropriate.
When you invite people to input their own definition of where they are they come up with a many different names for the same place - avoid it at all costs. I would suggest trying to pinch a breakdown from someone else or even buying it! - shocking I know.
