N.K.
Hi M.,
My parents have worked with Sit Means Sit training. They are based in the Phoenix area but will come to you. It is not cheap since they are private lessons with you and your dog in your home, but they work wonders. I think they also offer group training classes outside, but as far as I know they are all on the west side of the valley. That could have changed though, it would be worth checking into. Hope this helps! Good luck with your dog, it would be a shame to have to lose him. The training results will not be immediate, but with time and patience it will get better.
Also, I almost forgot to mention the Dog Whisperer shows with Cesar Millan. These have also helped make great improvements. He has great tips and advice for training. Cesar also has some books out, but I have never read any of them.