Mercy, I have to disagree with your reasons. To me it seems you are nitpicking on the photo for no particular reason.  Even if other religious beliefs (Muslims, Jews, etc) are represented the reality is that they are a very small minority when compared to Christians. Why not just have a collage of a few congregation sites (churches, mosques, etc) and eliminate the gallery altogether. To go over your points.
1)If Catholicism is the main religion then a Catholic Church should be prominently displayed.
2?Why not just change the caption.
3)What does it matter where the church is located? San Juan is after all the main population center. it's like talking about Italy and choosing not to display the Colosseum because it's in Rome.