NUS and SNU are both very good. Nanyang is good too. There is plenty to do there (eg night zoo is wonderful) and short trips (by bus to KL or ferry to Indonesia). Besides great food (ribs are excellent), there is plenty to see (and there is a good subway to get around on). There are some good quality hotels that are reasonably priced too. It will great to have your first foreign trip under your belt, Kay.