Hi Pauline
We have not stayed at the Hyde park inn but it is a 4 star hotel in a good location over looking Hyde Park it is just south of the main city square you could catch the airport train and get off at the Museum station and it would be a short walk to your hotel
To get to the city square you could walk 2 blocks west of your hotel and catch the Mono rail in Pitt Street and would take into the city the hotel does have a web site and gives a little info
Http://www.hydeparkinn.com.au
If I can help you any more just ask and I will try and help have a good time down under.