I love Nice, but cannot recommend a hostel but can advise what to see, depending on how long you are in Nice and what your interests are.
You can get a ride around the town in a little train that shows you the highlights of the town. You can pick this up on the sea front. I also recommend you visit the old town �Cours Saleya and to walk along the main Promenade des Anglais and take in the wonderful azure coloured sea. Note, there is no sand at Nice, just pebbles and one has to pay for using beach facilities. (If you want sand, go by bus/train to Juan les Pins where, if you look, there is some �free� beach.)
Outside of Nice, go to Cannes. If you are a nature lover, there are the Lerin Islands off Cannes which are easily accessible by boat � Saint-Honorat and Sainte-Marguerite.
Also outside Nice, although touristy, the very lovely hillside village of St Paul-de-Vence is worth a visit, as is the lovely hillside village of Eze. (You can get to both places from the Nice bus station.) Villefrance sur Mere is a quieter village on the coast near Nice which is very pretty. It can be reached by train and bus. Go to www.nicetourism.com for more information. Have a lovely time.