They don't always start at the same stop. I'm not sure what the loop is but it isn't always the same depending where the bus is coming from and going to. I know we had issues in Trinidad South (pirate rooms) so we walked down to Port Royale, got breakfast and got the bus there. It was often almost full still with Trinidad South and North to go so must have started in Jamaica. But then we got on at PR one morning and stopped at the Trinidads, Jamaica and I think Aruba too.
If I was to stay again I would request a room in a building in Jamaica or Aruba close to the walking bridge as they seem to be picked up first quite often and if they are last to be picked up it is just a short walk across to Port Royale and you can get the bus there. You are also close to all the amenities like the pool and restaurants.
CBR is gorgeous and we loved it, but the Trinidad South location was a bit far from the pool with two little ones after a long day at the park. The trade off was the pirate room which they adored and each island has its own quiet pool. Have a fab time.