Another vote for north kihei, in a condo with a kitchen if you can. sansei is good but be prepared to line up early on Sunday's and Monday's, ulua beach is good for free snorkeling, hit up the farmers market on the u of h campus for cheap produce/flowers/touristy gifts for family
The Indian restaurant (monsoon india) at menehune shores in kihei is a fantastic place to watch the sunset, but it is byob as they have no liquor lisence. Also, make sure you check out the flatbread company in paia, good pizza in an awesome little surf town. Da kitchen has a couple locations on island, each with their own menu, good for cheap food.
You really can't go wrong with Maui, it is a really good place to relax, and it can be done for quite a reasonable price if you know what to look for.
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