If I'm running my App Engine app on localhost, will I not see a value for X-AppEngine-Country?

According to the Release Notes:

All user request have an X-AppEngine-Country header which contains the ISO-3166-1开发者_如何学JAVA alpha-2 country code for the user, based on the IP address of the client request.

My app is running on localhost with the 1.5.1 Java release which contains the X-AppEngine-Country header but I don't seem to be receiving any value for this header in my requests.

Do I have to deploy the app to a production instance to test this feature?

Yes. Geolocation is provided by an internal Google service, which isn't available in the development environment.