If you set prologues := 1 in the mp file, that should help.
That still gave Courier fonts after including fig.1 in test.ps.
In a new metapost (texlive2007) you can even generate an image with the font included by using prologues := 3.
That worked. [I'm using MetaPost 0.993 (Web2C 7.5.6) from the Debian texlive2007-2 packages.]
From p.24 of the corresponding mpman.pdf manual:
It is worth noting that the default value prologues:=0 is sufficient for graphics included in TEX-based documents. Does that need a slight exception added to it? Or have I misconfigured something in the toolchain from .tex + .mp to .ps? By the way, the figure works fine with prologues := 0 if I include it (using epsf.tex) in a plain-TeX document. So I think there's something slightly off about what ConTeXt is doing. -Sanjoy `Not all those who wander are lost.' (J.R.R. Tolkien)