I show my dog and sit with a few ****zu people at shows. They are some of the most pampered and babied dogs when it comes to brushing and preparation for shows, but these ones still are obedient enough to sit on trolleys when they're told to, stand up when they're told to and don't move when they're told to.
All dogs can be obedient (even the small fluffy ones), it depends on the owners how much work actually gets done to make this possible. So even small fluffy dogs can be perfect angels!
I also lived with my aunt for a while when we were building our house, she has a 3 year old retriever x labrador which has had little training. It used to jump on everyone, snatch food, and basically not listen to anyone unless her dinner was in your hands. Our dogs aren't perfect but they do what they're told, and I found her dog quite annoying while we were living there, it some times made me angry. We were there for about 9 months all up, so overe that time I took it on myself to train her dog. I had her sitting and staying, she stopped jumping on everyone. Although my aunt still needed to walk her more often (which helps a lot) she was more controllable around the house. But walking a dog doesn't always seem a big thing, but the mental stimulation they get plays a huge role in their behaviour when at home.
So I understand your situation, but all you can do is become boss of this dog while it's in your care so it doesn't rule your life. If the other family doesn't want to fix it, they will have to live with the problems. Dogs live by a ranking system, if they feel they are higher than you they wont listen, but as long as you sit higher in the chain you will be ok till it goes home. The loud chain and "bah" ideas above are a good idea. They do work, but consistancy is going to be your best friend.