Hi, I actually live in Waltham. What area are you living in? There are really only two areas to do anything. Main Street and Moody Street. Main street has some fast food restaurants mainly, as well as the library, a yoga studio, and the post office. Moody Street seems to be getting a bit nicer, there are lots of nice restaurants and some stores. There is also a path along the river where you can walk, although I have yet to go down there. There are also two train stops with access to Boston, buses to Boston, and in Newton (next town over) there are 2 accessible subway stops.
It's a suburban city, it's a good place to live as a stepping stone to something else, we have been here for about a year and a half and a friend of mine just moved here because of it's convenience.