I'm from UK and it all depends the difference between the US release and the UK release, for example if it was release in US 23rd March and then more than a month later in UK about 30th April or longer, then i'd pre-order from US but if it was released in UK about 10 days after US then i'd be out buying it instantly, i'd first to buy it, can't wait for this! :)
One thing for sure, the day it comes out here in the UK will be the day I buy it, I might even buy both Black & White... even though I have White in japanese and will probally be getting the third game (if there is one :P)