They require very little care on a daily basis, and actually can be left for a day or two with planning, although it's always a good idea to chick on animals daily if possible, of course. There is no reason they should smell, with planning. Hens will squawk an "egg song," usually, but in general are quiet, and some breeds are quieter than others. Yes, they can get diseases, although there is little danger to humans, again with a little knowledge and common sense. If you purchase from a reputable source, you could have chickens for 20 or 30 years and never see a disease. I've had them off and on all my life and never have, other than one insignificant virus (fowl pox.)
That said, I would never recommend getting them where they are illegal -- although people certainly do it, especially if their neighbors are agreeable. In our Local Chicken Laws and Ordinances, you will find a lot of material about the arguments for allowing chickens, and stories of people who have gotten their law changed. There is a real movement out there toward this. A few short generations ago, the government was encouraging everyone to keep a few chickens. In Michigan, there is a state right to farm law which overrides local laws against keeping chickens.
I would encourage you to try to get your law changed.