For dressing, mash half of the avocado. Stir together mashed avocado, sour cream, lemon juice, celery salt and hot pepper sauce. Stir in milk til desired consistency. Cover and chill while preparing salad.
For salad, combine spinach, garbanzo beans, tomatoes, cucumber, cauliflower, mushrooms, onion and walnuts. Slice one hard boiled egg and add to salad. Slice remaining avocado half, brush with additional lemon juice if desired, and add to salad. Top with dressing and toss to mix. Cut the remaining egg into wedges and use to garnish salad.