My 5 yr old son who was diagnosed as PDD-NOS/possible Asperger's and the school assessed him for ADHD, and said that he has the characteristics, talks all of the time too. He is either talking, singing out loud, making noises, clapping, he is very rarely quiet. He can talk in perfect sentences, that make perfect sense, but he also likes to babble and make up silly words and ask repetitive questions, and repeat stuff that he has heard over and over----It is driving us crazy!! ! I adore my little boy, and like you, and am so very grateful that he is verbal, but man, sometimes I wish he could give it a rest! He has issues with this at school too, and I am afraid that if he can't get it under control, that they will want to continue to place him in special ed courses. I wish I knew what to do about it!
Good luck, and hopefully, someone else can give some advice!