Complex sentence: Most South Africans in the United States are currently settled in San Diego, CA: approximately 20,000 people, although they are elsewhere in the western United States and in the Pacific Northwest these cities lack significant numbers of South African Americans.
Split into simpler sentences: Most South Africans in the United States are currently settled in San Diego, CA, approximately 20,000 people. Although they are elsewhere in the western United States including the Pacific Northwest, these cities lack significant numbers of South African Americans.