Can the Tamron 18-270mm F/3.5-6.3 Di II VC PZD mounted to the Nikon D5100?

I just bought a Nikon D5100 with 18-55 mm lens. I have read about the Tamron lens and I want to know if this a good lens.

If you get it in the Nikon version, then it will mount just fine on your camera. Be aware that it's also sold for Canon and possibly Sony.

It's a versatile superzoom, but the image quality won't be that good - that's a typical problem of superzooms.

Here you can compare it to the Nikkor 18-200mm. Move the mouse over the sample shot to switch between the Nikon (mouse not over the shot) and the Tamron (mouse over the shot).
http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=667&Camera=614&Sample=0&FLI=0&API=2&LensComp=492&CameraComp=474&SampleComp=0&FLIComp=0&APIComp=2
Note that you can choose different focal lengths and aperture settings there. You should always compare similar values there.

If you're a newbie and got used to point-and-shoot zoom terms, then yes, the 18-270mm would be absolutely amazing. If you consider glass quality however, it would be very poor. The longer the zoom, the worse the lens. Primes are the best.

If you decide to get the Tamron, make sure you order one with a Nikon mount. Tamron makes lenses for different camera brands.

As others have stated, you need the Nikon-compatible model to be compatible with the D5100.
As for the question of whether it would autofocus with the D5100, yes it would.
As seen at http://www.bhphotovideo.com/...Di_II.html
it has "Piezo Drive Ultrasonic AF Motor".
I think that the gorgeous 16 megapixels of the D5100 would magnify the deficiencies of this lens. It would be better to spend the money on a 16-85mm AF-S VR.