Simon, I am sorry you are having problems joining Yuku. The address you posted would be an Email address ... if that is where you went then you wouldn't be able to sign up.
Click the link Trekker gave in her post and it will take you directly to the main page. Up at the top of the page is "Sign Up" in black. Click on that and it will take you through the process. You'll have to wait for an activation Email before you can post.
If you still have the same problem and get something back that says Diabetes Living isn't in their system, would you copy and paste exactly what you get? I will report it to Yuku support.
Thanks and good luck. We sure want you to join the group.
Suzanna