Definitely call beforehand and ask if they offer day rates. Facilities are reserved for overnight guests only. The only exception is they do give complimentary access to all facilities prior to your check-in time and after your check-out time, but only on day of your arrival/departure. Obviously, this is done for capacity control reasons, as the facilities are built to hold x number of guests.
FYI, I believe it's spelled out in our Owner's Agreement that we are only entitled to use the facilities when we are using our Vacation Ownership Interest (VOI). As is appropriate, since as one Tugger pointed out during the last discussion on this topic, many people live within driving distance of SVO resorts, and allowing them to come and use the pools at their whim would interfere with others' rights to enjoy the property during their VOI. Presumably, you gave up your use week, which means that someone else (renter, exchanger, your guest) is using the resort in your stead.
Hope this helps. Have a great time in Orlando!