Definitely, these are some wonderful places to visit in France! I am happy to provide some travel tips:

Best Time to Visit:
The best time to visit Nice, Cannes, and Avignon is during the spring months from April to June and the fall months from September to October. The weather during this time is mild, and there are fewer crowds.

Route and Accessibility:
Upon arrival at Nice Côte d'Azur Airport, you will find easy connection to Cannes and Avignon by train or car. France has a well-developed train network (SNCF). The drive from Nice to Cannes is around 30 minutes, while the drive to Avignon is around 2.5 hours.

Altitude and Acclimatization:
All three cities are at near sea level, so altitude sickness is not an issue.

Accommodation and Booking:
There's a variety of accommodations in each city - from luxury hotels to budget hostels. It's always recommended to book in advance, especially during the Cannes Film Festival. In Avignon, staying within the city walls can provide easy access to most attractions.

Clothing and Essentials:
Pack comfortable clothing suitable for walking. Carry a sunblock as the sun can be quite strong, a reusable water bottle, and a good pair of walking shoes.

Health and Safety:
Standard European health and safety rules apply. It's advisable to have travel insurance that covers health and theft.

Local Etiquette and Respect:
French people take great pride in their language, so learning a few basic French phrases can be helpful. When entering shops or restaurants, it's polite to greet with a 'Bonjour' (during the day) or 'Bonsoir' (evening). Remember to respect local customs and traditions.