Two things come to my mind:

1) Do you think most tourists (be it in Sao Paulo or elsewhere) can speak the local language? Read it? Do the signs need to be very visual to make even sense?

2) Isn't there still a huge difference between the number of times you actually found an ad helpful ("Ah, okay.. Let's go there") vs. awkward, boring, distracting?

I especially like the first one. This country has less people than Sao Paulo. In fact, the local language is probably spoken (and read) by less people than those living in Sao Paulo. Billboards are everywhere, including hotlines, shortcodes, directions - and I cannot understand a single one. I'd argue that the average tourist here wouldn't care about the ads. They are for residents/citizens.