Most folks in Buenos Aries get by without guns because few criminals have them.
If you knew as much about Ayn and as you pretend to, you might know that she did not advocate carrying guns:
Question to Ayn Rand: What is your opinion of gun control laws?
Answer by Ayn Rand: "I do not know enough about it to have an opinion, except to say that it is not of primary importance. Forbidding guns or registering them is not going to stop criminals from having them; nor is it a great threat to the private, non-criminal citizen if he has to register the fact that he has a gun. It is not an important issue, unless you're ready to begin a private uprising right now, which isn't very practical." [Ford Hall Forum, 1971]
Question to Ayn Rand: What's your attitude toward gun control?
Answer by Ayn Rand: "It is a complex, technical issue in the philosophy of law. Handguns are instruments for killing people -- they are not carried for hunting animals -- and you have no right to kill people. You do have the right to self-defense, however. I don't know how the issue is going to be resolved to protect you without giving you the privilege to kill people at whim."
[Ford Hall Forum, 1973]
A great deal has changed since the early 1970's when she answered the above questions (in the United States).
Though she advocated the right to self defense, Ayn Rand's philosophy had absolutely nothing to do with the decision I made whether or not to own a gun where I now live.
PS: I've never known an Ayn Rand fan who owned a gun.