18 days in Spain in October

I am very biased on this topic - believing no amount of time in Spain is sufficient. Eighteen days is good, though. Regarding your list of cities.....all can be reached by Spain's excellent public transport. I wouldn't travel in the order you have them listed (for example, Cordoba is between Sevilla and Toledo, Ronda is between Sevilla and Granada, etc.) - but your list is fine. The days allotted per city is a personal preference and adding Barcelona is a little out of the way by rail...but certainly a worthwhile addition.

I would revise in the following manner:

Fly in
Madrid (day trip to Segovia) - 3 nights
AVE Train to
Toledo - 2 nights
AVE Train via Atocha
Cordoba - 2 nights
AVE Train to
Sevilla - 4 nights
ALSA Bus to
Ronda - 1 night
ALSA Bus to
Granada - 2 nights
Low-cost flight to
Barcelona (day trip to Girona or Tarragona) - 5 nights
Fly out

Good Plan -----

I agree with Carlos that you need 4 nights in Seville. It is a beautiful city with many important historical sites and is also a wonderful place to wander slowly and savor its beautiful plazas, fountains, parks, etc.

Five nights is better than 4 nights for Barcelona. I’m not sure you have time for a day trip. It all depends on what you want to see in Barcelona. Keep in mind that many of the important sites, especially the Gaudi sites, require advance purchase tickets. This makes it harder to see a lot of sites in one day.

If you like art, I think 4 nights is better for Madrid than 3 nights, especially if you want to spend time in Madrid’s outstanding art museums, such as the Prado, Reina Sofia, and Thyssen. There are other interesting places in Madrid, too, such as Retiro Park, Palacio Real, Temple of Debod, etc.

And you are wise to visit Andalusia in October rather than during the very, very hot summer months. The temperatures should be very pleasant for sightseeing; Seville might still be warm but not unbearably so.

Check www.bahn.com for train schedules:
Madrid 3 nights - includes a day trip to Toledo by train (45m).
Sevilla 2 nights - 2h 45m train.
Ronda 2 nights - 2h bus ride.
Cordoba 2 nights - 2h train.
Granada 3 nights - 2h 45m train.
Fly nonstop to Barcelona (check Skyscanner) or take a 6h 15m train.
Barcelona 4 nights - that includes day trips to Montserrat and Dali's Museum in Figures (buy your ticket before leaving home).
Fly nonstop to San Sebastian or take a 5h 45m train.
San Sebastian 2 nights.

I like Carlos's plan a lot.

I don't travel the way MaryPat does. I think one full day and a few hours in Seville is grossly short (that's what 2 nights gets you), as is 1 full day and some partial days in Barcelona--which is what would be left with side-trips to both Montserrat and Figueres. Three nights in Madrid with a day-trip to Toledo is just one non-jetlagged day in Madrid; that would be OK for those who don't plan to step inside an art museum or go to Segovia, but the OP wants to go to Segovia.

I like the Basque Country, but I cannot recommend traveling there from Barcelona (or Madrid) for just two nights. Those nights are desperately needed for Seville and Barcelona. A super-short side trip to San Sebastian is way too much travel for way too little time in place, and getting out of the San Sebastian or Bilbao airports is likely to be more costly than flying home from Barcelona or Madrid.

Thanks for your suggestions. Do you know if the AVE train will go from Granada to Barcelona? I've read that the new track/routes should be operating by October but can't find any details. The only flight I can find is on Vueling and the reviews are really bad.

There is AVE service now, so I don't see any reason why it wouldn't be available in October. Depending on what time you want to leave, you many need to change trains, apparently at Antequera.

You won't be able to see the October schedule for quite some time, but go to Renfe.com and check the schedule for next week for the day you plan to travel, using Barcelona-Sants as your destination:

https://www.renfe.com/EN/viajeros/index.html

I looked at a couple of weekdays and found a 7:10 AM departure (connecting in Antequera) and a 3:45 PM direct train that doesn't require a connection. The afternoon departure gets you to Barcelona at 10 PM.

Those same departures are on the schedule through April. It appears that if you monitor the Renfe website (probably not necessary until late May or early June) and buy your tickets when they first go on sale, you'll be able to get the afternoon train for no more than 60 euros. The early-morning train may cost more like 82 euros.

Renfe's website is a bit odd about connections. It appears that you could leave Granada later in the morning or early in the afternoon, spend a bit longer on the train, but arrive substantially earlier than 10 PM. If the prospect of a 7:10 AM departure doesn't please you, you probably have two later options. The late-morning train requires three connections, which would be annoying (and possibly stressful if you have much luggage); the early-afternoon train has only one connection, in Antequera. However, if you had to buy separate tickets for the two legs of the early-afternoon train because they are not coupled on Renfe's website. I don't know what would happen if the first train was late, causing you to miss the second one.

You can take a look at the connections Renfe isn't publicizing on the Deutsche Bahn website.

Carlos has a great plan, though you could shift one day from Barcelona to Madrid. (Carlos is from Barcelona, so his preference is understandable.) Ronda is fine but one night is really enough. I agree that San Sebastian is "a bridge too far" on this trip. As for bad Vueling reviews, how bad can such a short flight be? Seems like it would be much better than a train ride that takes basically all day -- as good as Spain's trains are.