Will, I know the area very well. Grew up there and still invests in the area. 'Upper Vailsburg' is often referred to as 'Ivy Hill' and really starts west of sanford avenue on up into South Orange (the area borders Seton Hall University). Whether or not the crime is "high" there depends on what you're accustomed to and what you're comparing the area to.
If you're comparing the area to the rest of Newark, it's pretty low. But compare it to the suburban towns neighboring the area, Maplewood and South Orange, and it's ok. Personally, if I was really concerned with the crime but wanted to stay in Newark, I wouldn't mess with anything North of 18th Avenue and East of Sanford Avenue (look on the map and you'll see what I'm talking about). Good luck.