Absolutely! Traveling to the south-west of France would be a wonderful experience. Here are a few tips for your journey to Biarritz, Bayonne, Lourdes, and Toulouse:

Best Time to Visit:
The best time to visit these places is during the late Spring to early Fall, specifically from May to October when the weather is warm and pleasant.

Route and Accessibility:
You can easily reach Biarritz by train from Paris (takes around 4-5 hours). From Biarritz, Bayonne is just a short drive away. Lourdes and Toulouse are also well connected by train services.

Altitude and Acclimatization:
These cities are not located at high altitudes, hence no specific acclimatization is required.

Accommodation and Booking:
There are a range of accommodations available from luxury hotels to budget hostels. It's advisable to book accommodations in advance, particularly if you're traveling during the peak summer months.

Clothing and Essentials:
Light, comfortable clothing is suitable for the summer months, but always pack a rain jacket or umbrella because showers can be unpredictable.

Health and Safety:
Carry standard travel insurance. The tap water is safe to drink and healthcare facilities are excellent. All cities are pretty safe, but as with anywhere, take basic precautions especially while in busy tourist areas or at night.

Local Etiquette and Respect:
French societal norms apply. Be courteous, remember to say "Bonjour" (Good Day) and "Merci" (Thank you). Also respect the local customs, particularly while visiting religious places like the Lourdes Sanctuary. French is the local language, so having a basic understanding or a translation app could be advantageous.