I have a JPEG image that is currently gold and white. I need to turn this into a 1 bit monochrome black and white SVG (the gold should become black) so that I can do foil printing. I have noticed that the gold part contains lots of slightly different color variations and a lot of the white is really very light grey. Is there a way to filter this into two colors using Inkscape?

Technically you can, using the Trace Bitmap feature and playing with the tolerances.

But in this case you could use the right tool for the right job, which is to use a raster editor (GIMP, Photoshop, Paint.net) to adjust it to B&W. After you've done that you could put it into Inkscape and used the Trace Bitmap feature.

If you're not familiar with how to use a raster editor to achieve this, you will want to convert it to greyscale, then play with the brightness/contrast of the image. Turn the contrast up high then play with the brightness to find the compromise of Black to white ratio.

^--Exactly.

See this topic:
http://www.inkscapeforum.com/viewtopic.php?f=5&t=14070

You can use gimp for adjusting the colours to be like a monochrome one,
but it's more likely you can't avoid manual tracing for the finest result in inkscape.

Post the image so that we can be more specific.