I haven't been to Rio yet. I'm going to try to go in January when I'm in Buenos Aires. Can Americans still go without a visa? I know they were going to change it so Americans had to get a visa but I think they postponed it.
I have been to Mexico City a few times and didn't see any at all. Probably some exist but I didn't see any in my trips there. I was surprised in BA they were everywhere! No matter which neighborhood I was walking around in I saw some in Belgrano, Recoleta, all over Palermo. Was interesting seeing so many around on various neighborhoods. The only place I didn't see any is in Puerto Madero. But then again there weren't too many mini markets there.
I went to Osaka there would night and a normal store near there but didn't see any chinos.
I don't think there are many in Mexico City. Probably some but I have been there a few times but mostly just in the touristy areas and didn't see any. I have been to Rio a few times but didn't see any.