Place the potatoes in a large pot and cover with water by several inches. Bring to a boil over medium-high heat, then reduce to a simmer and cook until the potatoes are tender, 12 to 15 minutes. Drain, then let cool completely and cut in half.
Place half of the avocado and 1/4 teaspoon salt in a large bowl and use a fork to mash until partially smooth. Add the cooked potatoes along with the cilantro, olive oil, lime juice, red onion, garlic, half of the bacon, 1/4 cup scallions, the remaining avocado and salt and pepper to taste.
Stir to combine, then transfer to a serving dish and garnish with the remaining bacon and 2 tablespoons scallions.