I would be taking the pup out socialising , but i wouldnt be putting it on the floor or on a bus seat for that matter.

I took bily out to socialise before all hi jabs were fully done, but he was either carried or he sat on the back seat (tandem seat) of my sons buggy. He wasnt ever allowed to go to the floor etc! He got to meet lots of people and I went to play with friends and family's dogs who i knew were fully vaccinated. HTH xx