According to a Eurogamer Spain interview (translation) with Microsoft PR & Event Manager Lidia Pitzalis, Kinect will not support voice control in all regions when it launches this November. At launch, according to Pitzalis, voice control will be available in the US, UK, Mexico and Japan.
Eurogamer Spain notes that speaking English (or Spanish with a Mexican accent) won't suffice either, as voice control will actually be disabled in the affected countries at launch. Spain and other launch countries, including France, Germany, Italy and even Canada, will have to wait for a Spring 2011 update to enable the voice control features. For those without an internet connection, the update will be provided on future games and via "other solutions that do not involve an additional cost."
Update: Microsoft has informed Shacknews that Kinect will support voice controls for English-speaking Canadians at launch. Voice controls for French Canadians, however, will arrive in the Spring 2011 update.