Then let me educate you Shan because where dogs are concerned, I will never shove off. They're my life, my work and consume my spare time too. So, whilst I would never call myself an expert, I do happen to know a thing or two about dogs, as do many on here who have spoken out about Millan.
There is NO SUCH THING as a "good breed" for a family. I know of gentle, affectionate German Shepherds and arsey Labradors (and own both), snappy Jack Russells and soppy Staffies. There is no more sense or safety in deciding on a dog for your family on breed than there is deciding to trust a Jamaican over a Japanese man or vice versa.
Which brings me to terriers. The same applies. Consider the individual personality, not the breed. You wouldn't want my Lab near your kids - he isn't fond of them, yet my 3 yo old Shep would adore them... but surely it's supposed to be the other way round...? Yes bull terriers have a "reputation". That's because bad news sells newspapers. My kids are rescue volunteers - on an average day they can interact with maybe 20 or 30 Bull breeds and they are still in one piece. Have you ever heard of them? No? You won't either... because them not getting hurt isn't news.
WRT a guard dog, think again. The best "guard" is a dog that barks. That's all the average family need. (So, you wouldn't want my Shep after all - he's huge and looks the part but is generally silent!). Unless you are willing to pay thousands - literally - for a ready trained dog or in training a dog up (and remember the dog you chose may not be suited to security/guarding purposes), then forget it. A poorly taught "guard dog", one which is encouraged towards aggression by novices in the expectation that their pet will guard them as well as being a friend, is a potential danger and certainly not to be relied upon when the going gets tough. A dog which barks sufficiently to frighten the shit out of a potential intruder/someone coming down the path is more than sufficient for normal households as he will be a deterrent.
BTW, to the person who asked what CM would think of their Bull breed cross, there is one thing to be said in his favour. One of his own dogs )if not more) was an American Pit Bull Terrier, so I guess we can assume he isn't hung up about bull breeds. :)