Unfortunately, I believe that your dreads will drastically limit your chances of getting into a reputable firm. For the vast majority of firms, image and professionalism is very important. It is sad that you may be overlooked because of your hairstyle, but I am afraid that this is the grim reality. However, if it is worth it to you to keep your dreads, I am sure that if you are a good lawyer, and are persistent about finding a good firm who will accept you as you are, I think you can find one eventually, but it will be much more difficult.