Hi Jason,
Yes just showing up during opening hours should be fine. The site isn't remote so unlike the places in the middle of the desert you will surely find someone around.
Entrance was free but you pay for the guide which is necessary because he knows where the rock art is plus he will drive you around the site.
Have fun on your trip.

Thanks Zoe, appreciate all the helpful advice!

Zoe
Hi Zoe -- Did you have any travel guides with you in Saudi? I'm just wondering if you think it's fine to bring the Lonely Planet guide to Saudi Arabia and/or Lonely Planet guide to Oman, UAE & Arabian Peninsula (the latter guide warns that ``many books'' may be considered problematic by customs). I would be grateful for any guidance. Thanks!

I use ebooks so I wouldn't know, although I don't even remember customs checking my bag at all. What do those books contain that goes against Muslim beliefs?

Zoe
I don't think there is any issue with material in the books related to religious beliefs; I just wasn't sure how carefully customs looks at books. It sounds like it won't be a problem. Thanks again for all your helpful guidance.

Zoe
Hi. Just returned from our trip, and we had no issues. I just wanted to say thanks again for the tips. Best, Jason.

Madain Saleh still closed for restoration?

clyde
My research has led me to believe that it is officially closed until Oct 2020 or thereabouts, but they are opening Madain Saleh to tourists during the Winter in Tantora festival from Dec 19th to Mar 7th. You can buy tickets for tours online. I don't know if these tours are the only way to get in there during that time or if you can do it on your own. I'm going in Feb.

I got into Maden Saleh last year, but it was with a special government trip. While the site could use some work, it wasn't that bad. It could use a new road and some new signs.

I just returned from Saudi Arabia, the country that, after so many years of isolation, unexpectedly reopened for vaccinated Westerners. In 9 days I drove almost 6000 kilometers, having visited all WHS and all but two TWHS (unvisited ones were Al-Faw and Uruq Bani Muarid. I could easily accommodate at least Al-Faw, but preferred to visit other places of interest near Riyadh). My itinerary was as follows:
Day 1 – arrival in Dammam, Al-Ahsa WHS, overnight in Riyadh
Day 2 – Turaif WHS early morning, then to Fayd TWHS, overnight in Hail
Day 3 – the longest day during my trip (over 1000 km driven) - very early departure to Jubbah (Hail Rock Art WHS), then to Dumat Al-Jandal (IMO the best TWHS in KSA), overnight in Al-Ula, where I went through Al Khanafah and Tayma
Day 4 – early visit to Al-Ula Old Town (Syrian Hajj Road TWHS) and Al-Ula Hijaz Railway Station TWHS, first bus to Mada'in Salih (my 500th WHS, woo hoo!), back to Al-Ula at around noon, long drive to Yanbu (TWHS Egyptian Hajj Road), then to Jeddah, where I've visited its unique Historic District WHS
Day 5 – Jabal Shada Reserve (the steepest road I have ever driven!), Zee Ain TWHS and Rijal Almaa TWHS, overnight near Abha, close to KSA's highest peak
Day 6 – drive to Jazan, free ferry to Farasan Islands TWHS, overnight there
Day 7 – first ferry back to Jazan, picturesque road to Najran through Dhahran Al Janud, visit to Hima Wells WHS, then looooong way to Riyadh, taking some rest in the car somewhere near Wadi ad-Dawasir
Day 8 – early arrival to Riyadh, visit to the Edge of the World, perhaps the best natural site in KSA.
Day 9 – Riyadh, late departure to Europe

A couple of thoughts:
Driving in KSA:
1. Almost all car rental companies have very low mileage limit – usually 200 km per day. For me it was far too low, but I have found at least two companies where you can buy unlimited mileage for less than 10 EUR per day. I used Key Car Rental and may recommend them.
2. Saudi Arabia is one of the easiest countries to drive, its road system is excellent. Roads that appear on Google Maps as peripheral – check e.g. the one that goes through Al Khanafah reserve - are in fact wide and comfortable. However, beware of numerous speed cameras, that can be found even in the middle of the desert!
3. The only place where I had to pay for parking was Historic Jeddah. Even in the very center of Riyadh it was free!
4. Gasoline management is important. It was no issue in the densely populated southwestern part, but in the north I drove over 200km without any petrol station!
5. Learn Arabic numbers, as speed limits are frequently shown only in Arabic.
6. Obvious advice - don't go on dirt roads with 2WD. I got stuck near Asfar Lake (part of Al-Ahsa WHS) and had to walk quite a bit to search for assistance. I managed to visit the Edge of the World, but the road there is certainly not for 2WD cars – reaching this was perhaps the most difficult driving experience in my life.

Other tips:
1. All Saudi WHS are now open, however, you need a special (and very difficult to obtain) permit to visit Turaif. Fortunately, this place is clearly visible from the opposite side of the road.
2. KSA is one of the most pleasant countries for foreign travellers on tighter budget. The only place where I had to buy entrance tickets was Mada'in Salih, all other WHS and TWHS were free. The 2h ferry to Farasan Islands was free of charge even for cars!
3. However, KSA still seems to be unprepared for tourist traffic. In Hima there were no signs or WHS logo, without help of locals you won't find any rock art! TWHS village of Zee Ain was completely empty.
4. The country works well to improve its tourist spots and in a couple of years it will be much different. There are TWHS that have potential for inscription – No 1 is Dumat Al-Jandal, but also Rijal Almaa and Hajj roads.