Note I have never built numpy or scipy, Though another admin I worked with has tried and had all sorts of issues, with acml, atlas and others.
That being said, if you just need cblas why not build cblas for acml? It is easy. cblas is just a wrapper around the fortran calls,
I blogged about building cblas with acml a while back:
Though I would still love to acml to ship with cblas already....
Oh and if you REALLY want to get down and dirty, you can use ar to unpack libacml.a and cblas.a and then make a NEW libacml.a with ar again using the .o (object files) from both. Can make life simpler,
Let me know if you have trouble with building cblas.