Rhebogue isn't gangland by any means, but there is ahalting site behind one of the estates (anglers walk). drominbeg is quite a big estate and houses will be cheaper there, and I haven't heard anything bad about the place it just seems very sparse there.
The castletroy - students thing shouldn't put you off, because generally students are located around the university, in allocated student accom., or around the briarfield area.
Look at Bloomfield and newtown in Annacotty, anywhere in monaleen (more expensive though), and Caislean na hAbhann in castletroy. All good estates, no students, no social housing (that I know of at least) and still all a handy drive to the Parkway.