I have a Nikon N70. The lens is a Tokina AT-X PRO 28-70 f2.6. I am interested in a Nikon D5100. Will this lens work with the D5100? I appreciate any information provided.
The d5100 will mount almost every nikon and nikon mount lens there is. The aspects that may or may not work, depending on the lens, are autofocus and metering.
There are several versions of that Tokina lens. No doubt the lens will mount on a D5100 and you will make photographs with it.
The "baby" Nikon's (D40, D40x,D60,D3000, D3100, D5000, D5100) were built as compact DSLR's so they would appeal to women, and do not have an auto focus screw drive in the camera body.
Consequently, if your Tokina lens does not have an internal auto focus motor you will only have manual focusing with the Tokina mounted on a Nikon D5100.
The Tokina will not AF with a D5100. It should meter but I had an issue once with a Sigma 24-60 and D7000. I've also read about other's with similar issues.