Flying to Cannes doesn't have to be too expensive, depending on how early you book and the routes you take. Obviously the most popular choice is to fly into the Nice airport. However, to cut down on costs, you can also fly into neighbouring airports in other parts of France (such as Lyon, Marseille, or Toulouse) or Italy (Genoa or Turin), and then either rent a car or take the train to Cannes. This sometimes works out cheaper overall, but you have to decide if the added hassle is worth it.
Yes, fly into Nice (aer lingus) and get either the bus outside the terminal exit door for a few euros or walk across and take train. Short pleasent journey as stated.