Heat the olive oil in a small skillet over medium-high heat until hot but not smoking. Add the guanciale and cook, stirring occasionally, until it is just about crispy, 5 to 6 minutes. Add the garlic and cook, stirring a few time, an additional minute. Set aside to cool slightly.
Put the cannellini and pinto beans in a serving bowl. Add the guanciale and garlic and all the renderings in the skillet, along with the tomatoes and mint, and stir to combine. Season with salt and pepper. Serve at room temperature.