Piscataway, like so many Central NJ towns, has no discernible downtown.
It is also not noted for restaurants.
Overall, it is a decent & safe place to live, but I don't think that it fits most of your criteria.
You might want to take a look at Somerville, which is the county seat for Somerset County. (Piscataway is in neighboring Middlesex County). Somerville has been "gentrifying" for the past several years, and it has a constantly-developing, walkable downtown with a number of good restaurants. Because it has a small...not-so-good area...the crime rate is higher than in...let's say...Piscataway...but the crime rate is still low, overall. Somerville is a town on the way up, so to speak, and it also features an active art community.
Highland Park also comes to mind. Its downtown is not as nice as that of Somerville, IMHO, but it is walkable, and the town is definitely safe.
The only other places that I can think of in Central NJ with "downtowns" are New Brunswick (which has a high crime rate), Woodbridge, and Princeton. Personally, I am not particularly fond of Woodbridge, but it does have a small downtown area and it offers good accessibility to NYC--if that is important to you.
Princeton is not really close to Piscataway, but it is within commuting distance, and has a very nice downtown, a few very good restaurants, and an extremely low crime rate. Additionally, the campus of Princeton University is a beautiful and historic place to take walks, and the campus also features the (free) Princeton U. Art Museum and the excellent McCarter theater.