I've had a "little" experience with cockatiels, and parakeets. Parakeets CAN talk (most people dont know that) ..but its rare. I had one that would say "no". and that was all he decided to learn. Cockatiels speaking are depending upon thier personality. If you spend A LOT of time with them, talk to them in a voice they like (they will turn thier head sideways at you)...and repeat repeat repeat...they WILL eventually talk to you. some depending on personality will only repeat one or two words, and the rest will be SOUNDS, like the sink dripping, the dog barking, the alarm clock. ect. And some will do word, after word, and rarely do SOUNDS. it just depends on the bird, and what its individual personality likes.
They also make tapes you can play while you are away to "teach" the bird those sounds. I've not found them too succesfull truthfully.
As to not biting.
All depends. If you start out with an older bird, that wasnt handled very often..your in for some work. And you will likely get bitten a few times.
I've found what "helps" is NOT to yank your hand away when they bite. Its hard..because that is our human nature to remove our hands from pain..but it "teaches" the bird very quickly how to "avoid" contact..and get the nasty humans hand away.
It dosent TEACH the bird to be friendly.
So...if bird bites...keep hand still..and usually a quick blow of air on thier face, or taking thier top beak and saying "NO BITE" and removing it from your hand is a good way to start.
My mother had a cockatiel that was a HARD biter (usually cockatiels dont bite hard)...but he would draw blood. Finally figured out that he was "cage" territorial. If you allowed him to COME OUT on his own, and then offered your hand..he'd hop right on and was sweet as pie. You reach in his cage..you were getting a bloody finger. In fact..his name was JAWS (lol)
Birds are VERY social creatures..and if you want the bird (or parrot) to bond with YOU..its best kept single. However IF your are not going to spend ALOT of time with it..and are at work most of the day. PLEASE get it a cage mate (same species)..or dont get it at all.
They either need YOU alot, or A FEATHERY FRIEND alot.
a solo bird that dosent have much interaction with its human is very very depressed bird.
ALso please know that birds in general are VERY sensative to household items, scents, ect...good rule of thumb is to RESEARCH everything you can about them . BEFORE you bring them home.