Hi,
There are a couple of launderettes in town that I know of - probably a few more but I haven't tended to look for one.
There's definitely one on the Avenida ( the road running along the front alongside the river) not far from the footbridge to the marina and there's a dry cleaners at Pingo Doce supermarket on the eastern edge of town, but I'm not sure if it's a launderette as well.If you will have a car, then it'll be no problem but it's a bit of a hike without a car.
The Vilabranca is just opposite a residential area where they have their own shops etc so it may be worthwhile checking there before making the long haul into town:go straight across the road as you come out of Vilabranca, turn first right and first left and you will see a small supermarket and a row of shops - there may or may not be a launderette among these.
Hope this helps a little.

Thanks very much.