Clean conch, tenderize, and chop into half-inch pieces. Juice limes, lemon, and orange and add to conch. Add onion, bell peppers, celery, salt, pepper, and Tabasco. Mix to combine flavors and refrigerate for four to six hours or overnight. One hour before serving, add tomato and cucumber. Serve on a bed of salad greens, and garnish with avocado slices drizzled with lemon juice.