The area around St Andre is ideal for both disciplines with quiet roads generally well surfaced with great views . There are numerous forest tracks and bridleways ideal for Mountain biking. 
Nearby Allos has an exciting downhill course accessed by chair lift or take the novel way and ride up, but be warned the second section is 'a bit of an Effort'.
Mountain bikes are available for hire locally and I keep 4 or 5 that can be used for non technical rides and for trips to the village, lake or river.
Call or e-mail me for details of special two centre cycling holidays in St Andre and Alp d'Huez for club cyclists.
This is a special all inclusive holiday.
Fly to Nice and spend four days based at Chez Ray exploring the local area then ride to Alp d'Huez with one or two overnight stops. Spend three days riding some of the famous Cols in the area before returning to Nice via Chez Ray.
Cost 450 pounds including transfers, accomodation, breakfasts and evening meals.