The Spar would be your cheapest option, It´s on C/ Pedro Barba (where I used to live!!!

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As the above post says, out of your apartments turn right down the hill, turn first left at the supermarket. Down the hill and to the crossroads, Ladyline Tattoo shop there, then left again and up to Spar, looking at 5 mins.
If you need car hire, turn right at the tattoo studio, head to the front and you´ll see Plus Car office on your right, Maria is great and gives great deals.