The menu notes that all pupusas are GF. I had a concern about the tortillas they serve and the fried tilapia, but they have a huge vat of masa they can make tortillas from and assured me they did not use wheat flour. I ordered a pupusa (served with cabbage salad and spicy salsa), as well as a corn (filling) tamal. They were both very good.
They offer GF pupusas, which are clearly marked on their menu.