Reference: Collins Robert Unabridged Spanish/English Dictionary

español term (edited): el santo y seña

The phrase is "santo y seña" and it literally means watchword. In other words, in this case "we would give each other the word about the place to be"

It's a saying. It can mean different things. I' leaving an article in Spanish with all the different meanings.

It was used in the military like a kind of password to identify the enemy. It changed everytime so soldiers had to tell each other the "santo y seña" so if they were asked to identify themselves, they could answer with the right word. Now it's symbolic, like to tell someone something really important, like a keyword or a code. I don't know if I have made myself clear.

So in your paragraph, porteños pass on the information to each other about a good bar and then they meet there.

I'll try and think about other options. But do you get the idea?

español term (edited): el santo y seña

No doubt in my mind regarding the meaning and use of "santo y seña". The question regarding the accuracy of its use in the context provided remains open.