I trained my first vizsla puppy in agility as we were concurrently learning obedience. He was between 5-6 months old. The best part was how easy it was to initially train him. The worst part was when he went through "fear stages" and would fall off an obstacle and be afraid to get back on. It would take me weeks to train the fear out of him. At age 2 he developed systemic inflammation and has not trained anything since - he is 9 now and has been the BEST dog ever! We never got to compete in anything and now, that is ok. We are getting a new puppy in about 8 weeks (just born 3 days ago!) and THIS time, I will do obedience with her first and we are not going to start agility until she is 1.5 - 2 years old. My last non-vizsla dog, a border collie mix, was 2 when we started agility and she was never fearful and only fell off one obstacle ever. I think it is a good age for such a demanding sport - I'm also a certified canine massage therapist and hope by waiting we will have a long agility career.
This is just my experience...have fun no matter what you do. 