1. Place lemons in small saucepan, and cover with water, weighting lemons down if necessary to keep submerged. Bring water to a boil, reduce heat to medium-low, and simmer 30 minutes, or until lemons are tender when pierced with knife tip. Discard water, and cool lemons.
2. Meanwhile, cook quinoa according to package directions. Remove from heat, scatter snow peas and currants over top, cover, and let stand 3 minutes, or until snow peas are steamed. Transfer to large bowl, and cool.
3. Cut lemons in half, scoop out pulp between segment membranes, and remove seeds. Place pulp in bowl, and scrape out and discard all remaining pith, membranes, and seeds from lemon skins. Cut lemon skins into 1/4-inch-thick strips, then slice into small diamonds. Add to lemon pulp along with onion, oil, sugar, and 1 Tbs. water. Let stand 10 minutes.
4. Stir lemon mixture and avocado into quinoa mixture, and season with salt and pepper, if desired. Stir in arugula just before serving.