Papas Rancheras Tacos in LA????
I don't know how regional papas rancheras are, but Homestate appears to serve various Texan foods. They aren't on the menu, but you could ask if they will make it special.
Other than that could you describe papas rancheras? Ingredients? How they are cooked (soft like boiled potatoes, crispy like home fries etc) and what particularly you like about them?
Even if the real thing doesn't exist out here, someone might be able to find a similar dish.