Should we buy tickets ahead for Toledo Cathedral?

In mid-October I doubt you’d need to purchase ahead of time. If you had a few extra minutes after the cathedral, stop by the nearby “pozo amargo,” (bitter well). It’s just a well on Calle Pozo Amargo and only takes a couple minutes to see. The tragic legend of the well is a (shortened) Christian fell in love with a Jewish girl, was found out, and murdered. The girl cried into the well and her tears turned the water bitter. One day she she thought she saw him appear in the well and she threw herself into it to be with him. If you can get there and there are no cars, it makes for a nice photo.

There’s also a legend about the Bridge of San Martín. The bridge is very pretty.

Edited:if you didn’t want to take a taxi from the train station, there is also an escalator that will take you to the historic center. It is just past Puerta de Bisagra. On Google maps look for “Remonte Mecánico Peatonal de Recaredo / Toledo escalator” Across the street from the escalator are the remains of the seldom visited Roman Circus. Not much left, but good for a few minutes.

No need to buy in advance. Tickets are available right across the street from the entrance on Calle Cardinal Cisneros. If I remember correctly you have to leave an ID card or pay a deposit to get the audioguide. This insures you will return them. The cathedral is very beautiful, spectacular and in my opinion one of the prettiest in all of Spain. I have visited Toledo at least 8 times because I have a friend who lives nearby. Great town for wandering the streets. If you have any interest in paintings by El Greco, you can do a quick visit at the Santo Tome church to see the famous painting titled, The Burial of the Count of Orgaz. Since you only have one day, I assume you may be daytripping in by train from Madrid. The interior of the train station is quite pretty. A daytrip by train is easy to do but it is quite an uphill hike to get to the historic city center. Take a bus or taxi. The gates to the city are very picturesque. Try to at least see the Bisagra Gate. If you do not have a car I highly recommend you ride the little tourist tram that takes you to see the scenic vistas of the city from across the Tajo River or pay a taxi to take you so you can actually stop to admire the views. There are several lookout points where the entire city is spread out before you in all its glory. Don't miss it. If you are staying overnight, you are in for a treat because Toledo is quite pretty when illuminated at night.

Thanks for the help and suggestions!