Since Suzan lives in Cotacachi I’ll defer to her on this one. My friends in Cuenca with cats have no problem buying litter, so I can’t imagine the situation is different there.
Yes, I have two cats and I can get cat litter here. You have to buy it when you see it though as it’s not the most common product. But our two local stores in Cotacachi now carry it as well as the local vet. You can get it many places in Quito and I’ve also bought it in Otavalo but it took some looking.