from the MBJ website: http://www.mbjairport.com/passenger-services

'Red Cap' Porter Service

Red Cap Porter Services are available at all times to the travelling public at both the Departures and Arrivals for a minimum fee of US$ 1.00 per bag.

Efficient and courteous porters will assist passengers in moving their bags from:

Departures – from curbside of the terminal building to the airline check-in position;
Ground Transportation Arrivals Hall to a point at curbside appropriate for obtaining the type of transportation required by the traveller.

I have both let the porter take my bag, and rolled my own out to the shuttle... If I'm going somewhere and they already have the bag on the cart - like sandals- I don't mind.... but if I can do it myself and no one offers, I just roll myself out to the bus!