Personally, I'd be worried about any restaurant that misspelled the word "jocon". And, as for the Ceviche, very, very few Guatemalans would consider putting ketchup, or "salsa dulce" as we call it, into something as sublime as ceviche. And, it's generally considered acceptable to each the dish on saltines, or perhaps, tostados, or corn chips. As much as I love my Guatemalan tortillas, combining them with ceviche wouldn't make any sense.
And yes, I do live in Guatemala.