The Masuda method is possible because of an internal marker on each Pokémon which identifies their "home location", 0x17. If the game recognizes the two Pokémon in the daycare as having different home locations, then the chances of the Egg hatching into a Shiny Pokémon will increase. In Pokémon Diamond, Pearl, Platinum, HeartGold, and SoulSilver, the odds will be increased by five times: from the usual 1/8192 to 1/1639. In Pokémon Black and White, the odds were increased again, to 1/1366. This is six times as likely as encountering a Shiny Pokémon in tall grass. - Bulbapedia
If you read the bold it says that 2 Pokemon with a different home location, meaning where you are is irrelevant, so long as the Pokemon being bred have different home locations.