Feb and March can vary widely weatherwise. The further south you go, the warmer is going to be. The further away you are from the coast the more chance you can get snow. Daytime temperature will be suitable for biking (50-60°F or 11-16°C), and nights are going to be cold (although unlikely subfreezing especially on the coast). As for the route, as long as you stay away from the main raods you will have a blast. Every region has its own particularities and you'll find beautiful sceneray pretty much everywhere. I personally love the Calbria Region and Sardegna Island. Enjoy!