If you move across the main street to the "market place" and in the area of the "Place Pigalle Go Go Bar" you will find one or another beggars.
Ladies of the night is very discret in SB compared to GS. I saw some this year, but they wont approach you if you walk with your companion.
But then again, if you want to get to them, just walk alone outside e.g. Disco Lazur in the middle of the night... I was waiting for my wife one late night (or maybe morning

) and were approached. But, showing them my wedding ring and a naugt with my head made them dissapear.