PWPs require two spaces between them.
Placing larger PWPs like the bus stop (which is 4x2) can be tricky, though. I think what I did for the bus stop was have Isabelle stand where the bottom, second-to-left tile would be, then talk to her from below. Like so:
x x x x
x I x x
-O
I being Isabelle, O being me, x's being the spaces the bus stop would take up.
So if you're putting the bus stop to the left of the cafe, there would have to be four spaces between Isabelle and the cafe. If it's going to be on the right, you'd only need to put Isabelle three spaces away. Hopefully that makes sense.

I can draw up a diagram in Paint if it's unclear.