Whenever I have taken the bus to Downtown Disney it has made three stops. First at the Marketplace, then Pleasure Island, then the West side. The west side area where they drop you off is behind Cirque du Soleil so it might actually be a quicker walk to get dropped off at Pleasure Island, not sure though.
I would tell the bus driver when you board where you want to go and see what s/he suggests (or if they didn't intend to drive there for some reason might consider it).