If I understand your question correctly, the answer is yes.  It is also heavily used in Hong Kong as well.

Actually everybody from GZ speaks cantonese, even in official buildings, police, hospitals, etc...

Only the people from other provinces living in GZ don't speak it, but I know that many have learned it so as to be more easily accepted/considered.

But since they (the Cantonese) have learned mandarin at school, there's no problem...  And when addressing a gweilo they always speak in mandarin.

As for HK,  they don't learn mandarin at school, so they just talk cantonese

Yeah they speak it here! Cantonese is known as Guangdong hua or Bai hua. It is also a common language for people to speak in Chinese communities around the world, because a lot of migrants came from Guangdong.  They speak Cantonese in  (though not exclusively) in Malaysia and Singapore.

So the next time you order your Dim Sum in Vancouver, San Francisco or Melbourne, see if you can hear it!

Happy Days!

Actually,you can speak madarin in GZ,Even conton people can speak maderin .It is no problem.