if you do have guns in the house, and word spreads that you do have them, then your house becomes a more likely break in target for when you're not at home.
for those with sliding glass doors. most don't suffer broken glass; it it easier to either lift them up off the tracks, or break the usual chintzy lock. With the door open, drill some holes in the upper track and screw in some sheet metal screws. Let the screws hang down just enough so the door just slides; this should take care of door-lift.
Next, get some quarter round, or even a small in cross-section solid metal rod, and lay it down in the track. This will prevent the door from sliding open even when unlocked