The promenade between Nice's harbour and Cagnes sur Mer is so amazing ! I love to go there on a Sunday morning during spring or summer, when it's almost desert and you feel the sun rising on your skin, it's the most enjoyable feeling one can have ! It's also a nice idea for a romantic ride, as you can hire those bikes 24/24.
You can hire a bike for just the day for 5 euro with the VéloBleu system (http://www.velobleu.org/). Pick one of the stations on the coast or in the city, hire your bike and pay on the spot with your credit card and tally ho here you go !