We have a family friend who came over from Vietnam with my boys' grandparents. My Mom asked her the question recently circulating on a few Vn adoption lists about the appropriateness of calling HCMC "Saigon". Here is her response:

"Diep says Vietnamese people like to use Saigon, but it's totally acceptable and will not offend anyone to use Ho Chi Minh City. She also explained in her own way the following:

As the old name Saigon could not be abolished, the authorities conceded to a compromise and kept the name Saigon for the center of Ho Chi Minh City. Therefore the entire city officially is called Ho Chi Minh City, while the center officially is Saigon."