I learned dressage right off. I had no idea what riding really would be like, but I started off learning to be rhythmic, ride softly, and ride effectively as a dressage rider. I taught myself to be more of a hunter rider(big mistake) and am now back into hard dressage training.
I very much believe that dressage is a great thing for anyone to learn from a good instructor. If you know a good dressage trainer, I say go for it(: