"Are there any numbers on recent statewide Dem primaries..i.e....what % of enrolled dems come out?"
As of November of 2004, there were close to 4 million registered Democrats (and close to 3.4 million registered Republicans) in PA. See:
http://www.dos.state.pa.us/bcel/cwp/view.asp?a=1099&Q=444853&PM=1 In the 2002 Democrat gubernatorial primary between Bob Casey and Ed Rendell, a bit under 1.25 million Democrats voted (primary turnout in 2004 was much lower, since Kerry had already clinched the nomination and the Democrat Senate primary was not contested). Since there were around 3.76 million registered Democrats in May of 2002, Democrat primary turnout was 33%.