Hi
Not personally over as we are organising a large local event in the UK, however having just returned from Spain we have seen adverts in the free magazines for merchandise and some of the restaurants within the immediate surrounding area's are advertising events on the weekend/day.
Not seen anything specifically in San Juan and as rather a british thing, not sure this will happen. You may get someone like Annie's bar offering to do a bit of a street party!
Good luck and hope you enjoy the extended weekend.