I am not sure of the actual day's but there are markets at all the resorts on the costa brava, Calella, Pineda, Malgrat,

calella has 2 markets if i remember rightly.
i is at the far end of town, near where calella meets pineda, but you can get the noddy train from outside the olympic for about 2 euros return.cant remember what day it is on.
there is/was a smaller market on the main street on saturday mornings, where they have car parking during the week.