I've seen that Sunday afternoon one, I imagine it's still going on when the square isn't otherwise occupied with people in yellow and thugs with riot gear. You find sardanas all over the place.

Ball de bastons is much closer to morris than sardana is, but it's more a rural and small town thing.

You oughta try to hear a cobla performing - they play for sardana but also in concert. They range in technical ability up to a similar level as the best British brass bands.