How to ensure that ? I've got a lot of international traffic, too. I'm wondering if google also checks where the visitors are from. Because my site is in english and I'm from germany. When I look at my site I often see german ads. But of course I don't want my visitors from thailand to see german ads, too.
You see German ads because you are in Germany. Different visitor location = different ads and of cource different CPC. I have lots of international traffic also but whatever. I do not choose my visitors. Whoever wants to visits. The way you can check if there are ads for you in particular country...: go to google.com and search for the keywords of your site. Then when you have the results add &gl=XX, where XX is the country code for the coutry you are checking. Till now I only know "us" and "ca" but I will be searching for the others Added: Yeeeee. I think this is the list they use http://www.google.com/apis/adwords/developer/adwords_api_countries.html