Although black Democrats aren't necessarily liberals, I believe you are right. It would be a better Republican strategy to get the Green message out among the left and the blacks.
On a related note, just as Ralph Nader won Florida for Bush, imagine what a Cynthia McKinney 2004 Green Presidential run would do to the two-party competition. (She has been mentioned as a possibility.)
Facts:
1) There is no green party in Georgia.
2) Many Black voters are pissed off at the Democrats for taking them for granted-- the Mckinney thing.
3) Blacks hate Republicans more than Republicans hate Dems. They do not hate Libertarians in Georgia. The Parker Campaign in 2000 pulled more blacks than ever before, getting big votes (for Libertarians)in the black precincts.