We’ve restored the ability to signup and create new accounts on WP Engine (That was fast): http://wpengine.wordpress.com/2013/03/19/issue-with-signups-will-be-resolved-shortly/
I’ve just received word from our engineering team confirming the fix.
However, if you have any issues with a new account you tried to create in the last 30-60 minutes, please let us know by creating a support ticket and including the email you signed up with, as well as the account name inside of Zendesk, help.wpengine.com. If there were any bumps in the road, we’ll get them smoothed out so you can get on with your day ASAP.
Thanks for choosing WP Engine!