Truth is there are countless stereo-types given to each gender. My opinion is simple: all Cavalier King Charles Spaniels are smart and can be taught right from wrong and all puppies that are spayed or neutered around 6 months of age will not acquire the hormones that lead to marking.
Both genders are capable of marking. Males tend to mark if they come into contact with a female in season, while females that fall into the habit of marking may do it for odd reasons like being left alone or something. To get around this issue it is best to always crate train and when you are gone you will know your Cavalier King Charles Spaniel (dog) is safe from marking should marking become an issue.