Yes, snakes can carry salmonella. I don't know if every single individual carries it, but it's pretty hard to figure out if your snake does or not. And it can be transferred from your pet corn snake to you. Small children are more susceptible to it, though. That's why you should wash your hands when you're done handling your snake.
I really don't know the likelihood of getting salmonella from a corn snake, though, I just know that it's possible.