One other group to consider is SCMC (SVT Cobra Mustang Club). I know it sounds like mostly Cobras and GT500s, but they run (at least for the last two years) in conjunction with SVTOA. They have a nice mix of cars, mostly Fords, and any Focus would feel right at home.
But they are finished for this year at VIR, probably the next one would be next Memorial Day weekend.
'02 SVT Focus-new track toy
'98 Mustang Cobra-NASA TTB