i dont know about you guys but i got in not 2 mins ago.
this is what i did (hope it works for you)
on one tab i logged into gmail
on another tab i went to :
http://www.google.com/intl/en/+/demo/
and i clicked join the project button.
my email and name were already in it just asked me a couple things and next thing i knew i was in.
that was it.
hope it works for you guys LOL
maybe google just reopened free registration?
oh well gl guys