Karen2
HCM city and definately the area around the Hyatt is very safe. You might feel a bit overwhelmed by all the motorscooters, but you get used to it.
Compared to american cities after dark, you will find this a very comfortable environment. The hotel concierge will be able to help you with Vitetnamese restaurant choices. The chefs in the hotel are actually Italian (or at least european, so even that food will be OK).
The pic on the net is actually the entrance of the opera house next to the hotel
Compared to the Sheraton this will be an improvement.