Hello! It's great to hear that you're planning to visit Adana, Mardin, Hatay, and Sanliurfa. Here are some tips to help you with your travel planning.

Best Time to Visit:
The ideal time to visit these parts of Turkey is during spring and autumn months (April-June and September-November) due to favorable weather conditions. The temperatures during this time are pleasant, making it a great period for sightseeing.

Route and Accessibility:
Upon landing at Istanbul's international airport, you can take a domestic flight to Adana. From there, a mix of local bus services and trains connect between Adana, Mardin, Hatay, and Sanliurfa. Alternatively, renting a car could provide more flexibility.

Accommodation and Booking:
You can find a range of accommodation options in these cities. Online booking platforms like Booking.com and Airbnb are quite prominent for hotel and homestay options respectively. Remember to book in advance, especially during peak season.

Clothing and Essentials:
Pack comfortable clothing suitable for mild weather, such as light jackets and sweaters, as well as hats and sunglasses for daytime travel. Have your essential toiletries, medications, rain gear, and sturdy footwear for walking and exploration.

Health and Safety:
Make sure your routine vaccines are up to date before traveling. Use bottled water for drinking and be aware of local traffic rules when moving around. Carry a travel insurance for any unexpected incidents.

Local Etiquette and Respect:
Turkish people value politeness and customs. A friendly 'merhaba' (hello) and 'teşekkür ederim' (thank you) should always do the trick. Dress modestly, especially in religious places. Don't forget to remove your shoes before entering a mosque.