If you live in a high density, heterogeneous situation, you need an escape and evasion plan more than you need firepower.
I was in Buenos Aires on 26 March 1976. I have had the unfortunate occasion to witness the Liberty City Riot and the Rodney King Riot up close. I can assure you, if you start shooting during an urban disturbance, you will bring unwanted attention to yourself. You are much better off keeping a low profile and getting the heck out of there. You want something concealable but big enough that if you are confronted by people wishing you harm, it will put enough fear in them to let you pass.
And you need to realize that it is just not miscreants you need to worry about. The local authorities don't know you or your intentions. They just know if you start slinging lead, you are part of the problem, not part of the solution. The same perception will be shared by anyone in the general vicinity who is not aware of your specific preparations.
In the urban environment, discretion is the better part of valor.