I wasn't entirely sure if taquitos were authentically Mexican, but it turns out that they are mainly sold there as tacos dorados (and actually if they are made with flour tortillas, they are flautas). This version requires some fry time but they are relatively easy to throw together for an impromptu get-together.
Fill each tortilla triangle with a spoonful of beans, top with cheese, and a pinch or 2 of cilantro. (You don't want to over-stuff these or they won't roll up properly.)
Starting from the point side, roll the taquitos and secure with toothpicks. Heat the oil in a deep skillet and fry 4-5 taquitos at a time until golden and crispy on all sides. Drain on paper towels, remove the toothpicks, and serve warm with salsa, sour cream, and guacamole.