American Bulldogs are great breed. If you like the look and size that's a start. Educate your self on the pros & cons next. This is were you need to be very realistic and honest with yourself. An American bulldog is a molosser (mastiff) breed. They are not famous for trainability or fast response to commands.
If that's important look to the herding or field dogs.
With daily exercise they are calm in the house. Be honest about how much walking you are will into to do.
A responcible breeder studies the puppies during the 1st 8wks and they are the best one to pick the right puppy for you. That warm-fuzzy "my puppy picked me" is romantic silliness. That puppy that runs up a licked your face would mostly do that to everyone. For kids the breeder will help you find the puppies that are middle of the road temperament for that breed.
I find girl dogs to be easier to train. I'm not alone in that observation. Go to an agility or obedience completion there not a lot of male dogs to be found.
My female American Bulldog 'Bunny" was more than enough dog to proctect my home and was about 80-85#s.
After hearing more of your thoughts, you might also consider a Boxer.