Because DME it tied to your resort reservation, you can't be taken to a different resort..or picked up at one. If the resort you want to go to is on the same route your particular resort bus is using, then sure, you can hop off. For instance...you're staying at Pop but want to go to AKL....those two are usually on the same route so you could hop off the bus at AKL. Just keep in mind that any bags you have with you would ha ve to be taken off the bus when you got off.
Otherwise, no, you must be on the bus that goes to your particular resort.
You could, if you wanted to, and had no bags, get off at the first stop the bus makes and then either get a cab from there, or take a bus to AK and then transfer to the Polynesian bus. Or take a bus to MK and then boat or monorail to the Polynesian from there.