Whisk together first 5 ingredients to make dressing; set aside.
In large mixing bowl, combine avocado, orange, red onion, red bell pepper, cilantro, and jalapeno. Let stand for 30 minutes. Squeeze all liquid out of crabmeat. Check carefully for any shells. Add crabmeat to salad mixture.
Arrange lettuce on salad plates. Top with crabmeat mixture and reserved dressing. Season to taste with freshly ground pepper; garnish with orange segments if desired. Makes 6 servings.