excellent site
The people here will be happy to talk to you and give you lots of advice and info. They're very friendly and helpful.
I have three hens and they're not noisy at all, but can cluck a bit in the spring mornings and after they've laid an egg. Don't keep a cockerel in a domestic setting or the neighbours will not be happy. Cockerels also make noise all bloomin' day long, not just in the mornings.
Things you might need to know is that they need regular worming and you need to control external parasites as well or they can become debilitated.
Coccidiosis will manifest as constant diarrhoea, a mucky bum and being generally unwell.
Cleanliness is vital and keeping them clean can be a bit of a job. They need daily attention and cleaning. They produce quite a lot of poo which you will need to remove/sweep up, then swill down with water afterwards. I then sprinkle with a natural disinfectant called Stalosan.
If you go away, someone will need to come in twice a day to let them out/shut in at night, feed and give fresh water. Chickens aren't the kind of animal you can just leave for a day or two. Also, during the winter, their water freezes and needs thawing out a couple of times each day. Remember that it can be quite a miserable job cleaning up in the snow, wind and rain and you'll need to see to them even if you feel ill or tired. It can be a committment. My neighbours have just gotten rid of their hens due to the fact that they just couldn't spare the time to care for them and they also go away a lot. Remember also that friend/neighbours might not be keen on caring for them when you're on holiday - some people are funny about birds and bird poo 
Everything must be fox and rat proofed. You must also be able to ensure the chickens won't escape from their area.
Don't use hay in their nesting box - it grown mould if it becomes damp.
Chickens become sick and die very quickly - birds are designed to hide the fact that they're ill, so it can come as a bit of a shock. When in doubt, worm and treat for coccidiosis - these are the two most common reasons for disease. Use a product called Flubenvet to worm - just sprinkle a small amount on some catfood for seven days. Use Ivermectin drops for parasite control - you can get this from the vets. A product called Coxoid is okay for Coccidiosis.
The breed I can really recommend is called a Light Sussex - they're white with a speckledy black cape and tail. They're lovely and tame, cheeky, friendly, robust and good layers. You can buy various hybrids which are fairly resistant to disease as well.
Chickens make great pets and I love mine
Once you get into a routine, they're easy to care for and very funny 