1. Rinse and drain beans in a colander. Pick over beans and transfer to slow cooker.
2. Roast chiles over a gas flame or broil, turning with metal tongs, until just charred all over, about 3 minutes. Transfer to a bowl and tightly cover with plastic wrap. Let stand at room temperature 15 minutes. Remove plastic wrap and, using paper towels, rub skins off chiles; stem, halve, seed, and chop.
3. Cook bacon in a large skillet over moderate heat, turning, until crisp. Transfer to paper towels to drain, reserving fat in skillet. Crumble bacon and reserve for garnish.
4. Rinse pork and pat dry; season with salt and pepper. Heat reserved bacon fat in skillet over moderately high heat until hot but not smoking. Add ribs, in batches, and cook, turning, until browned on all sides, about 7 minutes. Transfer to a plate. Add onion, chiles, bell pepper, garlic, chili powder, cumin, and oregano; cook over moderate heat, stirring and scraping up any brown bits from bottom of skillet, 2 minutes. Transfer to slow cooker along with tomatoes with puree and the coffee. Nestle ribs in bean mixture and cook, covered, on low heat until ribs are very tender, about 6 hours. Pull meat from bones and discard bones. Stir in cilantro; salt and pepper to taste.
5. Ladle chili into serving bowls. Garnish with bacon, cilantro sprigs, lime wedges, avocado, and red onion. Makes 8 servings.