There's 2 different(possibly more but they aren't relevant) versions of the GRO website, http://ghostrecononline.uk.ubi.com/ and http://ghostrecononline.us.ubi.com/
If you are from the US and you go to the UK version of the site it will say you are in the queue, if you go to the US version however, you should be able to enter a key. The problem is the CVG keys wont work on the US version of the site anyway, so you're kinda stuck.
I have heard there's a way around it but I can't confirm weather or not this works:
1.Use a VPN program to change your VPN to a UK VPN.
2.Register a new account at http://ghostrecononline.uk.ubi.com/
3.check the email address you registered under to validate your account.
4.Click the apply for beta button and enter your key.
assuming that it works you should now be able to download and play the beta, but again, I cannot confirm if it works or not.