Hello!
I can't speak to the quality of the shops offered in the magazine or whether they are worth the time and effort. (Though, if they assignments offered to just about anybody, they likely are not that exciting.). Besides, I personally would never agree to do an assignment that I have not previewed.
Honestly, if you think you have the gist of how all this goes from your past experience, sign up for a small hand full of companies, find their job boards, and request an assignment or two. I suggest that you use the links at the bottom of this page to find companies. The "Most Discussed" companies are all large companies that have work nationwide and should have something near you, so they are often a very good place to start.
Hard work builds character and homework is good for your soul.