1. Halve and pit avocados. Score each avocado half 7 times lengthwise and 7 times crosswise to dice. Scoop out with soup spoon, and place avocado dice in large bowl. Reserve avocado shells.
2. Cut peel and pith from oranges with knife, then slice each orange into 4 slices. Cut each orange slice into 6 small triangular pieces. Add to bowl with diced avocado. Add radishes, romaine, green onions, lime juice, cilantro, and hot sauce (if using) to bowl. Season with salt and pepper, if desired, and gently toss to coat.
3. Scoop avocado mixture into avocado shells. Serve immediately.