Yeah, you can search in the message archives for some discussion about bouldering by bus. But the story is that there is boulder at York Redoubt right on the bus route, a coastal wall in Herring Cove below a look off right between the two bus routes (#15 and #20 - halfway between them - you'll see where on the transit map). And I think Kidston Lake in Spryfield is accessible by bus and some walking too, maybe two boulders there? Otherwise there is the Martello Tower in Point Pleasant... I haven't been to Herring Cove yet but I think it's the largest area by far of these.
I highly recommend coming to the Monday Night Bouldering and meeting some people with cars.
Jason