That depends on who you talk with.
There are people here who refer to it as “Saigon”. There are also people here who refer to the city as “Ho Chi Minh City”.
The difference in part, is whether the person is originally from here. I think those who are originally from here, still call it Saigon in part.
Those from the north, or who moved here, tend to refer to it as Ho Chi Minh City.
Officially it is Ho Chi Minh City, and you cannot go wrong saying that. But some do still call it Saigon, and there are still stores with that on their signs.
I think there are times when you should avoid referring to the city as Saigon. Maybe when talking with a government official you would want to say Ho Chi Minh just to be on the safe side.