Cruise passenger arrives In Shanghai for 2 days do I need a tour to qualify visa free

I am an American , I will be on a cruise starting in Hong Kong stopping in SH for 2 days then cruise to japan. I understand that qualifies for visa free , but what if we wanted to go ashore without a guide( I wanted to see colleagues in the city ) can we do that without a visa or do we have to be on a guided tour?

Thanks