I can't believe this is what my first comment on here is going to be about... I'm with OldHead. If someone makes the incredibly bad decision to break into my house, they will have to face the consequences of that decision. If they are armed, and in your house with the intent to commit a felony, there is zero chance of getting convicted of murder. The prosecutors in this state wouldn't even look at it twice. Point is: I have an obligation to protect my family, no matter what.
On the other hand, I don't think telling people about your grow is ever a good idea either. I understand that once you get the card you get a sense of security, but there are just too many criminals out there looking for people to rob. Your landlord does not need to be informed about your MMJ status, just like they don't need to know your HIV status. It's private info and none of their business.
I definitely don't claim to have all the answers, by any means. Just thought I'd chime in on this one.