Search results are localized based on the current user's country (IP based). You can override the country by passing a user token to the request to make sure you always get the same results.
About availability, it is track-based: if you want to know if the song is available in a country, you'll have to query each track from your album. For example, http://api.deezer.com/track/2150054 returns the list of available countries.