I’ve heard people call Old San Juan more Andalusian than Seville itself!
You are right, in aspect manners, customs and culture, PRs are mostly Andalusian, and the “minority” here who are descendants from the Castillians, Basques, Galicians, etc. of Northern Spain are the “blanquitos”.
Amen...God knows how many Castillian, etc friends I made in Colegio de Mayaguez, and they were all “blanquitos”