Cut the squid into small pieces. Place the tomatoes, bell peppers, and onions in a bowl. Stir together the vinegar, salt, pepper and 4 tablespoons of the olive oil to make a dressing. Pour this over the salad ingredients, and turn them until thoroughly coated. Heat the remaining oil in a skillet. Fry the squid and garlic until golden. Scatter them over the salad while still hot. Mix carefully and serve immediately.