Google+: Why does Google+ say that it is not available for Google apps when I try to sign up?

I created a gmail account with my enterprise email. Now I use it for all the apps: Calendar, Gmail, Docs, etc. I would like to register on Google+ using this account but when i enter a message says Google+ is not avaliable for Google apps. Google suggests start using it with a gmail account. But when my real account will be available, will i be able to transfer all the data?
http://www.google.com/support/+/...