When I was there a year and a half ago I went to a reasonable bar/cafe that did some pretty tasty Mexican food. And there's plenty to do and see in NP so you shouldn't get bored.

My Ex-Girlfriend is from New Plymouth.

Bar scene wise it depends on what you are into:
The Squeeze Bar= The name comes from the floor space available. Not for the claustrophobic.
Powderoom= swanky loungin' bar great to talk and sip. Better to visit earlier in the night rather than later. Worth a visit just to use the 'so clean you can eat off them' toilets.
The Grumpy Mole= Same format in every town.
Scruples= Karaoke bar. I think it is mandatory for all patrons to smoke.
The Mill= Meat market. Its reputation guarantees high attendance.
Off the beaten path/ Baja= The Mills 'less obvious' sister. In Tyler Durden fashion they have been known to flash segments of porn inbetween music videos.

Non-alcohol involved activities to do in Nupers:
* Mediarena is definitely cool.
* Real TART art gallery. Good concept and interesting to see every day Joe's art hanging along side more known taranaki artists work. All with resonable price tags.
* Puke Ariki Museum and Library.
* Climb Paratutu Rock. Wear sensible shoes.
* Walk along the foreshore or better yet have a go on the wind wand bike wagon thingy ma jigs.
* Go up the mountain
* Head around the coast to the Cape Egmont Light house.

Have fun!