I have increasingly noticed my British compatriots referring to places such as "Cancun, Mexico" or "Riga, Latvia" or even "Plymouth, Devon" in their spoken English.
As far as I am concerned, the above usage is suitable for use only on an envelope. I would always insert the word "in" between the city and the county or country in spoken English.
I wonder if this style is a recent American influence. I know that it is standard practice for Americans to refer to their cities using the format "city, state" in spoken American English.
I would be most interested to hear others' views on this!