Heat the oil in a large skillet over medium heat. Add the onion and bell pepper and cook, stirring occasionally, until softened, 5-7 minutes. Add the garlic and cook, stirring, for one more minute. Remove from heat.
In a large bowl, combine onion mixture, pinto beans, diced green chiles, cheese, and salt to taste.
If your tortillas are cold, you may want to warm them for 30 seconds in the microwave to make them more pliable. Lay one tortilla out on a clean work surface and cut into four equal triangles. Put a small spoonful of filling on each triangle. Starting from the pointy end, fold up, then fold both sides in and continue rolling tightly into a burrito. Lay seam side down on a lightly greased baking sheet. You may need to press down gently on each burrito to get it to stay put on it’s seam. Continue with the remaining tortillas and filling.
Bake the burritos at 350ºF for 12-14 minutes, until crisp and lightly browned.
Meanwhile, make the guacamole by mashing the avocado in a medium sized bowl. Add the onion, jalapeños, tomato, lime juice, salt, cilantro, and red pepper flakes if using. Stir to combine.
Serve the burritos warm with bowls of spicy guacamole, sour cream, and salsa for dipping if desired.
Nutritional information is an estimate for four burrito bites with guacamole.