We visited last week (thursday) and there was virtually nobody there, makes a nice change from the UK shopping centres.
If the Dos Mares centre near San Javier is anything to go by, sunday will be the busiest day of the week as nowhere else is open.
We came off at the same exit as Ikea and just followed the signs for the centro commercial , so I think you must be able to get to it from either junction.
I have posted some pics of the centre and the nearby Thader centre (next to Ikea).