Hello! It sounds like you're planning a wonderful trip to Nice, Cannes, and Avignon in France. Here are some travel tips for your journey.

Best Time to Visit:
The best time to visit these French cities is from April to June and September to November. During these periods, the weather is pleasant and there are fewer tourists.

Route and Accessibility:
Starting from Nice, you can take a train to Cannes which will take around 30 minutes. From Cannes, you can take another train to Avignon which will take about 3 hours. These cities are all easily accessible by train, bus, and car.

Accommodation and Booking:
There are plenty of lodging options available in Nice, Cannes, and Avignon, ranging from budget hostels to luxury hotels. It's recommended to book in advance through platforms like Booking.com or Airbnb, especially during the peak tourist season.

Clothing and Essentials:
Pack lightweight clothing for the warmer months and layers for the cooler months. Don't forget your swimsuit, sunscreen and a hat for the beach, and comfortable shoes for walking around the cities. Also, a power adapter may be needed for your electronics.

Health and Safety:
French cities are generally safe, but always remember to take general precautions to protect your personal belongings. The tap water is safe to drink in France and pharmacies are readily available for any health issues.

Local Etiquette and Respect:
French people value politeness, so remember to greet with a 'Bonjour' (Good day) or 'Bonsoir' (Good evening), and always say 'Merci' (Thank you). It is polite to greet shop owners when you enter and leave their shops.