Good decision to stay off the medication and use a change of lifestyle instead. Yoga will be great for you and also a great place to meet some girls
Another great idea would be karate. Check out your school, they probably have a club and have many beginners.
Fish is a great food that has been studied to improve memory. Stay clear of processed sugars, soda, coffee (I can't give up this one!) , and keep meat down to a minimum. Eat lots of Vegatables, fruits, and beans. Also there are places on campus that have strategies that have strategies for dealing with ADD.
My Dad and sister both have ADD. My Dad deals with it by keeping himself busy. He cuts the grass, about 2 acres, twice a week and likes to do gardening things. My sister is more of the creative type of ADD. My parents never put her on medication and she is getting better every year. I wish you luck and I agree with your decision.