We bought our Cali as an adult, and he's fine as long as its not too close to feeding day. Smulkin and our 13 year old handle him without any difficulty. Our durango is just a little baby, and he's musked me before when he didn't want to be held, and I was being persistent. I was amazed at the big smell that little animal put out. Our 14 year old handles him without much of a problem, though. He's pretty squirmy when you first take him out of the tank, though.
If you want a calmer king, go with an adult or subadult. Ask the breeder about its temperament - a good breeder will be up front with you. If you go with a pet store, ask the attendants to get the snake out - if the attendants look nervous, go elsewhere.