Most of Waltham is very safe. It depends on your preference as to style of housing, how far you'd like to be from
public transit, and the price of house that you prefer. It's a great location, and there's plenty to do here!
(and nearby). That being said, real estate values are pretty high compared to some areas west of here...
The north side feels more "suburban" and the south side has denser housing, and some of the houses are more
Good luck in your search!