Transport from Barajas Airport to Atocha Train Station

There are so many variables that I am not in a position to advise you about the timing. Maybe someone else will be willing to try. The usual advice is not to pre-purchase a non-refundable ticket for your arrival day, because so many different things can go wrong. Waiting to buy the train ticket after arrival does have its own risks, however: You will probably be paying the top fare, and there's a risk that the train you want to take will be sold out.

I opted to take a bus from the airport to Atocha. My hotel was nearby; I was not traveling beyond Madrid that day. In your case, since you're moving on by train, I think it would be smart to go straight to the train station at Barajas, where they'll sell you a suitable ticket to Barcelona. I do not recommend having your first ticket-buying experience at Atocha in a jetlagged/sleep-deprived state. That station is large and confusing, and the lines at the staffed counters are long. The vending machines are usually easier, but first you have to figure out which ones sell the ticket you need. Buying at Barajas avoids that problem.

This problem could have been avoided by buying a multi-city airline ticket into Barcelona and out of Madrid. That probably would not have cost significantly more than a round-trip to Madrid (which I asume is what you have). Just something to keep in mind for your next trip. A single ticket all the way to your desired first stop makes the airline responsible for getting you there with no guesswork on your part.

So forgive me for hijacking and asking what is probably a dumb question, but, @acraven, you said buy the train ticket at the Barajas train station. Is the train station within the airport? So I could take a train from the airport to Atocha and then to Sevilla?

There is a rail station at T4. Beyond that, I canot comment since I have never taken the train to or from Barajas. There's also a subway stop there. For those not immediately taking a train somewhere else, the airport bus or the subway may be simpler than the train.

Rick covers the logistics of getting into town from airports very well in all his guide books.

"So I could take a train from the airport to Atocha and then to Sevilla?"

Yes. And as a bonus, when you buy the ticket from Atocha to Seville, it includes a CombinadoCercanias, which is a code you can use to get a free ride on the cercanias (local) train from the airport to Atocha. Just ask for details when you buy the ticket.

As acraven says, to get from the airport to the center of Madrid, you have the options of cercanias train, subway, airport bus, and taxi. All can work well for various situations, but for getting from the airport to Atocha, the cercanias is probably fastest and easiest.

Thank you all for your help. We have purchased our train tickets to Barcelona through the Loco2 website and will probably travel by taxi from the airport tot Atocha. We have allowed 3 hours for all of this - wish us luck!