I would think it is Queso Fresco, sort of the Mexican version of a crumbly goat cheese, a little bit salty. Is this how it struck you? There's also Requeson, which is the Mexican version of Ricotta (more or less) and might compliment the sweetness of the plaintains better. Requeson is the creamier of the two but still something that could be crumbled. Hope this helps.
bjt
"eating is an agricultural act" wendell berry