How is the result of Tamron AF 70-300mm F/4-5.6 Di LD Macro with Nikon D3100?

Will auto-focus work in this lens with D3100. Does it perform well in macros?

The A17 model has a built-in motor so yes, that will autofocus. Performance is OK for a cheap telezoom. Macro is not exactly it's strong point to say the least.

I use this on the Sony A200, it is a good lens…

the "macro" is not a dedicated macro - just allows for a slightly closer magnification (focusing distance) between 180 and 300mm…

but if you want a macro - Tamron 90mm f/2.8 is a good lens…