The official language in Kaohsiung (Taiwan) is the Standard Chinese, but there are also the following recognised national and regional languages: Formosan languages, Hakka, Matsu dialect and Taiwanese Hokkien. It’s not very common to find a person who can speak fluently in English in Taiwan and so in Kaohsiung neither, but some young people will know and understand it.
The official currency in Kaohsiung (Taiwan) is the New Taiwan dollar (TWD). More or less, 1$ is 30 TWD. You can exchange your currency either in banks, in big shopping malls or in hotels. In Kaohsiung banks are usually open from 9:00h to 15:30h from Monday to Friday. Don’t forget to take your passport, so it is required for exchanging the currency.
It is recommended to spend at least one week in Kaohsiung, because it takes time to understand the culture and to explore its kept secrets, but if you don’t have an entire week, in 3 days you can see the most important and symbolic attractions of the city. If you get to know a local person from Kaohsiung who can show you around, it will be more efficient for sure.