We don't really have standards for the location fields, mostly because at this point we have no way of enforcing them. We do have a style page for them here, which we could add to, and hope that some people would follow the guidelines.
The first thing I'd add to there is that you should always include the country. This is an international site. I also think provinces and states should be spelled out, though that's less important if the country is included.
I think there are plans to improve the standardisation of the location fields, but I don't think it's a feature that's coming particularly soon, so in the meantime it would help if we could encourage people to follow style guidelines.