Jack,
I have no idea about regulations, license process, or public hunting area limitations - but - I can tell you where we saw pigs when we visited last year. My wife and I took a short 1/2 day hike along the Hau'ula Loop Trail on the windward side (maybe 40 miles from Honolulu) and saw 5 pigs. We never left the trail but all of the pigs were seen across a valley or down through the brush. There were signs indicating that this forest reserve was a public hunting area so this location may be a possibility? We also saw pigs right on a trail in the Waimea Valley Audobon Center, but getting permission there might me a challenge.