I don’t know the exact voter registration breakdown, but Cook rates the district as D+11, so it must lean heavily D. This district includes the city of Honolulu. Even if Djou wins the Special, he will have a tough battle in November to retain the seat for the 112th Congress.
http://en.wikipedia.org/wiki/Cook_Partisan_Voting_Index
Cook rates it D+11 because “hometown boy” Obama crushed McCain there in the anomalous 2008 election (in which Obama got 70% in the CD). However, in the more normal circumstances of 2004, President Bush got 47% in the district, and GOP Gov. Linda Lingle got over 53% and over 66% there in 2002 and 2006, respectively.