I haven't been to the sidewalk sales at OPO, but given the set-up there, my best guess is, they won't do it in typical 'sidewalk sale' fashion (where merchants put loads of sales items out on tables and racks on the sidewalk in front of their shop), but rather, will have a shopping center-wide sale, with each shop at OPO having special tables or racks with 'deep discounted' items.
It's a fancy way of saying 'all the stores are having sales Memorial Day Weekend'.