Rabaul a group of us hired a guy with a Hilux ute and toured WW2 sites etc. Seating in back was timber across the tray. It was great.
Alotau. We walked into town, the local markets and Milne Bay memorial. They were selling Beatle Nut everywhere. So all the natives had red mouths and rotten teeth.
The other islands were similar to small Pacific Islands. Great swimming Coral etc so if you snorkel take them.
John