I've just joined the AMA, think it was $75.00 US a year. To join any of the local flying clubs one has to be a member. A huge bonus for me was the insurance coverage. MODELAIRCRAFT.org
The AMA has a pretty strict set of rules, so I'm not so sure you'll be covered "wherever" you fly per that brochure. If you're flying primarily at AMA fields though, then it could be a great benefit for you.