Rent car or purchase bus tickets travel Granada to Ronda to La Linea to Tarifa to Seville

Try www.AutoEurope.com for rental rates. A lot depends on exactly what dates you want the car and how large a car you will need. Two passengers can fit in about any vehicle w/luggage, but four passengers will require a much larger and much more expensive vehicle. AutoEurope does show four-day rates for less than $200 for picking up a car in Granada and dropping it off in Sevilla. There is a disclaimer about one-way drop off fees.
Car rentals in Spain include some insurance coverage, but you will need to add a Collision Damage Waiver ( CDW) and Vehicle Theft coverage. One of my credit cards covered me for those two. You also need to have coverage for Personal Injury Liability in case you are at fault in an accident and people in the other car are injured.

Drivers of rental cars in Spain— if they don’t have a Spanish drivers license—are required by law to have an International Drivers Permit ( IDP). The IDP is a translation of your U.S. drivers license and it will have your photo just as your U.S. license has. You can get your IDP at any American Automobile Association (AAA) office for $30. Each driver of a rental car is legally required to have an IDP. Fines up to €500 and a lot of other serious complications can occur if you are pulled over by the police and do not have an IDP. Being in an accident without an IDP will void any insurance coverage you thought you had.

Buses in Spain are very modern, air-conditioned and quite comfortable. You will have a reserved seat and if you have luggage so large that you had to check it in at the airport, it will be safely stored below in the locked cargo hold of the bus. So, there’s room enough on buses in Spain for passengers to be comfortable. Don’t even think of Greyhound buses in the U.S, when thinking about taking a bus in Spain ( or anywhere else in Western Europe). The two experiences are like comparing night and day. Getting between the 4 towns in the sequence you have them listed is doable. If you take a three-hour train from Granada to Ronda, the fastest bus routings for your remaining three towns appear to be 2 hours, 1 hour, and 3 hours. In that case, the buses may be the way to go.
For bus schedules, check www.TheTrainline.com. ( Trainline shows train AND bus schedules and sells tickets for both). www.Busbud.com ( best for major cities).
and www.Omio.com. ( Omio also lists ride-share options such as BlaBlaCar).
Have fun in Spain!

Thank you for your very helpful reply!!

Decided to go the bus route. As we have gotten closer to arrival date, all except one bus route opened up for online purchases. Doing searches through sites like rome2rio were helpful in finding some routes and fleshing out the bus companies. Using that info I went to the individual bus company sites and was able to get schedules which allowed us to piecemeal trip from Ronda to La Linea at a decent hour--2 different bus companies. Using the company websites and paying in euros saved us a fair amount of money and gave us more control of the actual routes.

Looks like the tickets from La Linea to Tarifa are only sold on the bus. Does anyone know if the drivers take credit cards or just cash for that route--and, approximately how much the fare is?

Thank you in advance!

Good choice on taking the buses- that’s what I would choose with just 4 destinations 1-3 hours away from one another. You don’t need to worry about finding parking, refueling, looking at roadmaps or GPS, researching insurance requirements etc. etc. You won’t need an International Drivers Permit when you leave the driving to the bus drivers. Instead, you can look out the windows at the scenery and relax.
www.TGComes.es is the website of the bus company, Transportes Generales Comes, which has direct non-stop buses taking one hour for the run between La Linea and Tarifa.
It appears you pay the driver with cash or credit card when you board the bus.

Have a great trip!

@kenko Thank you for your thoughtful replies! Super helpful and insightful! Looking forward to the trip!

I just took a bus from Granada to La Linea. Then we took a bus from La Linea to Tarifa. The buses were very comfortable and convenient. After Tarifa we picked up a rental car in Algeciras. We drove to Arcos and spent the weekend there. We drove today from Arcos de La Frontera to Seville and dropped the car off at the St Justa train station. That part wasn’t fun but the drive was pleasant and beautiful.

Hello. :)))
I recommend the second plan of renting the car in Granada and dropping it off in Seville because going by bus can ruin your plan if you make a mistake with a connection.
Driving through Spain is not complicated if you go with your GPS. I only recommend that every time you enter a big city (Granada, Sevila) you forget that you have a car and use taxis/Uber because it is difficult to circulate in large cities. And the taxis are not goiung to be expensive. And car rental prices should not be exaggerated.
And that you rent cars with multinational companies that you have already worked with in your country, because the rules are the same as in your own country and that you do what you say. Catch it in Granada and drop it in Seville.
Those are the companies that rent cars in Granada. I would say all have also an office main station of Seville or Seville Airport.
https://www.kayak.es/Alquiler-de-coches-Granada-barato.27138.cars.ksp

Enjoy your trip.