(A true story.)   Meet Hola. She's a nightmare, but it's not her fault if she tackles strangers and chews on furniture, or if she runs after buses and fried chicken containers and drug dealers. No one ever told her not to. Worse yet, she scares her family. Hola may be the most beautiful Bernese mountain dog in the world, but she's never been trained. At least not by anyone who knew what he was doing.   Hola's supposed master, Marty, is a high-functioning alcoholic. A TV writer turned management consultant, Marty's in debt and out of shape; he's about to lose his job, and one day he emerges from a haze of peach-flavored vodka to find he's on the verge of losing his wife, Gloria, too, if he can't get his life--and his dog--under control.   Desperately trying to save his marriage, Marty throws himself headlong into the world of competitive dog training. Unfortunately, he knows even less than Hola, the only dog ever to be expelled from her puppy preschool twice. Somehow, together, they need to get through the American Kennel Club's rigorous Canine Good Citizen test. Of course, Hola first needs to learn how to sit.   It won't be easy. It certainly won't be pretty. But maybe, just maybe, there will be cheesecake.