I must reiterate that I think joining the AMA is imperative. I know many people have a great time for years without joining. I know also, that there are some other organizations which provide similar services and any one of them will do.
My primary reason for this position is simply the liability insurance coverage. Most homeowners policies do not cover modeling. Perhaps it is because I live in California, where the average person gets sued at least once before the age of 65. I would hate for you to lose your house because of an inadvertent crash into a group of kids or someone's prize Bull worth a million dollars or more.
Don't get me wrong, this is generally a safe hobby, but one plane through a school bus can ruin your whole day.
I wish you the best of luck, but don't risk all you have worked for to save $50 a year.
BubbaGates is right...you need to learn a lot more than controls to do this successfully. You will need to know what to do in order to safely start, tune and trim your plane. When to check the Rx pack voltage, what to do when a crash is inevitable.....the list goes on. A club and instructor will save you time, money and frustration. ALL AMA Chartered/Sanctioned clubs require membership in the AMA before lessons or flying privileges are offered. At least I think ALL of them do.
Best of luck to you.