I think only a specific niche knows about him, like the Budokai announcer who recognised him in the Boo saga, Baba fighters, Upa and his father, Suno and the village he saved... It'd be expected for the old Budokai audience to know him, but it's strange that they made no connection between Goten and little Goku who competed in the earlier Budokais. It's possible that the audience and spectators of the tournament changed once it became more like a festival in the 25th Budokai, too. The world king seemed to remember the kid who defeated Piccolo Daimao and the narrator stated that ppl had forgotten about the existence of Son Goku with Cell posing as a threat. I think overall he's so little known he wouldn't cause a commotion or anything by walking in the streets carefree.