France is an excellent place to bicycle and a fantastic country to visit - beauty extraordinare.
Nice is very nice. I've been there - so much to enjoy.
You shouldn't have any trouble finding or renting bikes. You can ask the hotel concierge (sp?) for assistance in locating a good rental shop, OR visit the local information office near the railroad station.
You should have a real ball! France has some very nice bicycle paths that go for miles and miles and miles - really functional for touring.