I'm not really sure what you mean by 'joiner fee'. Accor hotels has a program called Advantage Plus where you pay a fee for annual membership and get some sort of discount on all your stays and one free night. I get an absolutely fantastic rate at the Sofitel Grande, but that rate isn't available to the general public (not an Advantage Plus rate). If you got a great rate at the Sofitel Residences but can't come close to that rate with the Sofitel Grande or other similar options you may still want to stay at the Residences and just pay for motorcycle or regular taxis, as Transpac suggests. I generally only stay a few days but if you're staying for a month the difference in the rate could be quite substantial and more than make up for taking a taxi several times a day. December is a very busy month and they will likely not have any problems filling the rooms so the Sofitel Grande might not be willing to discount much for a monthly rate.