You are correct, at YUL you clear US customs at departure so your flight is considered domestic and you can have your luggages sent directly to your resort with DME (the terminal you will depart from is only for US-bound flights). My friend is also leaving for MCO in 2 weeks and she was telling that much of the flights to before Spring break to Orlando were late (evening flights). If it's your case, just be aware that your luggages might not arrive in your room before the middle of the night if you let DME take care of them for you!