Bring a large pot of salted water to a boil. Add potatoes and cook until tender but not mushy - approximately 15 minutes.
While potatoes are cooking, mix lemon juice, garlic, salt, pepper, balsamic vinegar, and olive oil together in a large bowl.
Drain potatoes and run under cold water briefly. Transfer to bowl and stir. Add arugula, bacon, and green onion and mix well. Serve immediately, room temperature, or cold.
Notes
If you don't want the arugula slightly wilted, cool potatoes completely before mixing ingredients.