We are flying into Madrid from the US, arriving at 8:25 am. We plan to take a bus from Madrid to Granada that day. Should I reserve seats in advance? Buses leave at 10:30, 11:30 and 14:00 from Estacion Sur. If we buy tickets at 11:30 (think this gives us enough time for arrival and transport to bus station), are they flexible in case we are delayed for any reason? In other words, if I miss the 11:30, could I trade for the 14:00?

Since all of the seats on these ALSA buses are reserved, if you miss your bus, you will have to purchase tickets on the next bus, if seats are available.

Unless you happen to be one of the first off the plane and have carry-on only, I would look at the 11:30 departure, which can still be tight unless you take a taxi in from the airport. Even in a taxi, I would allow at least 30 minutes from the airport to Estacion Sur. The airport bus does not stop at Estacion Sur.

'arriving at 8:25 am.' - I would not be purchasing ahead and with the number of buses from 1130 onward I would not be concerned.

Thank you for your responses. I have a followup question. Because of a medical condition, it is highly desirable to have a restroom on board whatever transportation we use for long distances (more than an hour). So, are there restrooms on the ALSA buses?

The ALSA website does not indicate there are restrooms on any of its buses.

https://www.alsa.es/en/services/alsa...hType=national

I am afraid the restroom query may be definitely maybe. I have no doubt I have travelled on ALSA buses with and without a toilet.

As an afterthought I went to the ALSA sight - top right is 'What do you need ?'
Simply entering 'toilet' gives me - 'THe vast majority of our normal-class buses destined for large routes have a WC. Of course, all our buses in the Supra Class and Eurobus have a W.C.'