Alrighty...
Condition One: Round in chamber, hammer back, saftey off
Condition One-A: Same as above, but with saftey on
Condition Two: Round in chamber, hammer down
Condition Three: Chamber empty
In a 1911, carrying with the hammer down is unadvisable. While the inertial firing pin will still prevent the weapon from going off if dropped on the hammer spur, the 1911 lacks any sort of decock function, which means you have to lower the hammer manually. If you do that, you're doing it at your own risk, as if you slip, you can only hope that the half-cock position will stop the hammer from hitting the firing pin. An accidental discharge can get you in all kinds of trouble.
Furthermore, the 1911 isn't designed to have the hammer manipulated manually. At least on my 1911, which has an extended grip saftey, the hammer is hard to reach with your firing hand thumb, and in a pinch, the time delay can get you in trouble.
Carrying a 1911 locked and cocked is perfectly safe. THREE things need to happen before a 1911 can fire. A), the grip saftey has to be squeezed. 2), the saftey has to be flicked off, and C), the trigger has to be pulled. With the saftey off, the trigger CANNOT be pulled unless the grip saftey is pressed in, and in order to do that, you need to have a positive grip on the firearm. If you're still nervous about it, just carry condition three, but practice practice practice the "Israeli Draw", making the racking of the slide habitually part of drawing your pistol.
And, since you asked, you can't flick on the saftey on any 1911 that I know of without the hammer being back.
Hope this helps! All this coming from a guy whose never carried before, and the 1911 is the only pistol I've ever shot! You sure learn a lot here at TFL!