well I live in Shenzhen too (live and work in Nanshan) and I hear Cantonese and Teochew on the streets daily. You can hear people speaking Cantonese all over the place: in markets, in office building elevators, restaurants, etc. In certain areas you can hear tons of Teochew being spoken as well (most electronics markets and wet markets seem to be run by people from Chaoshan), which is another regional culture with a strong identity that's strongly resisting getting wiped out.