WILL GOING TO ONE CLASS A WEEK BE WORTH IT?

If you are asking yourself  this question, then the answer is YES. Why? Because if you do, it then becomes a habit. It becomes something you will commit to. Going to one class is more of a mental and emotional exercise than a physical one. If this is the question in your head, tell yourself: "One class is what I can do right now and that will then lead to more (classes, swimming, running, cycling, walking....whatever!)". It is the right step. You will feel proud - such an important thing to feel. Everyone starts somewhere. Your steps don't have to be gigantic. You just need to keep moving forward. Be better than you were yesterday. Committing to exercise is the biggest challenge. If one class is what you can do, then so be it. 
TURN THE THOUGHT OF DOING ONE CLASS AS BEING USELESS INTO THE THOUGHT THAT IT WILL BE THE START OF SOMETHING AMAZING FOR YOU.
If you are at a point where one class is the only option and you think that you won't gain anything from it - THINK AGAIN! 
You know you won't see any major physical changes in your body. You won't lose inches or see muscle toning if you are working out for one hour a week (you will feel pretty damn good after, though). But to me, that's not the reason why you should go to that one class. You go because you need to be that person who commits to the action of going to a class. You are building a foundation. You commit to it and follow through. THEN you feel better about yourself. Understand and be kind to yourself! Don't feel shitty because you can only do one class. Feel awesome that you can!!
Once you create the habit, you will find more time and energy to fit in more classes or other forms of exercise. Then the physical changes begin. 
YOU CAN DO IT. BE THAT PERSON   :)