Best,safest, most economical way to get from Seville to Cadiz when buses and trains are all booked

Don’t limit yourself to trains leaving from Seville Santa Justa station. There are many more trains that leave from Seville San Bernardo to Cadiz than from Santa Justa. Plenty of availability..

That’s very unusual for trains, and buses, to be sold out a month in advance for this route.

When will you be traveling?

One can usually book buses 2-3 weeks out.
Check here for buses: www.tgcomes.es

Thank you for the suggestions...only 7:30 PM train on June 4 - so I lose a whole day in Cadiz :(
NO BUSES at all on June 4

According to the bus website, tgcomes.es,
tickets for June 4 will be available soon.

One can book tickets up to June 1 now, so you should be able to book your ticket for June 4 in a few days

If busses and trains sold out months in advance they would be useless. Public transit is used by people to go about their every day business, and those displacements typically are not planned months in advance.

So what you are seeing is that bookings are not available yet.

For example I just looked at Seville to Cadiz today, and I see about 10 trains between now and midnight, and tickets are available for all of them.

This is how you go about planning grond transportation in Europe: Always look at today, as well as at your actual date. If you see huge differences you are just to early to book.

Those are regular buses with several daily connections and it´s part of the public transport net, so in most cases you will not need a reservation, they run frequently every day and it´s as easy as getting a ticket on arrival.

There are trains throughout the day, they take 1h42 min, and cost 16,65 when bought at the station. Nothing to worry about.
Buses are about the same price and the same time (no surprise...) so I would take the train if possible here.

Hello:

An alternative is to rent a car. The rental cost does not have to be excessive. Maybe 100 euros per day for a 5 seats car. By entering their websites you can check if there is availability and price, both in Seville and in Cádiz. One can rent the car in Seville and leave it in Cádiz.

If you rent in a working day the probability of having availability and a nice price is higher, In the week ends the demand is higher.

Getting around Spain with a rental car is not something very complicated if you have a GPS. The difficulty is in traveling through cities that are big where traffic becomes somewhat more chaotic. If you go with your GPS on the roads of Spain it can be a nice experience. And every time you enter a major city, let go of the car as soon as possible because that's where the difficulty is. Inside the city, forget about the car. You are already in the city.

When renting cars and for your peace of mind, use brands from international rental companies that you already know.

In Seville there are Enterprise, Avis, Hertz sixt, Europcar. I don't know if all of them also have an office in Cádiz, but it's a matter of looking. The rules for renting them are the same as those you have in your country of origin and the maintenance of the cars is very good and is an international standard.

Enjoy your trip.

If you go to the TGComes website https://www.tgcomes.es/ and plug in your itinerary, you will get "disponible próximamente" at the bottom of the schedule list. This means available soon. It looks like it is a less than 2 hour bus trip and will cost 17.5 euros. If you were able to get a ticket on Renfe (train) it looks like the transit time is similar.

Keep checking the website every day or so--I think we were finally able to book tickets 2-3 weeks out from our trip. Since the online ticket sales window hasn't opened yet, it is doubtful that they are sold out.

Sites like Omio or Rome2Rio are not exhaustive search engines/sources of route information. I do check them, but often try to visit the actual bus/train companies' website to find tickets. Some have great pages in English, others not so much--online translation dictionaries are extremely helpful in navigating the latter.

I would not trust Rome2Rio for anything except perhaps the name of the bus company serving the route. Maybe.