Hi there,
San Pedro is some 4-5 miles west of Marbella, and 2 miles west of Puerto Banus. There is a frequent bus service to Marbella. Do you know which area of San Pedro you may have found an apartment in? If somewhere is described as "beachside" it generally means south of the n-340 road, as oppossed to "beachfront" if its by the sea. One of the local journalists described San Pedro as "the Chelsea of Marbella" on the former Living In Spain TV Channel.
Best Wishes
Roland