Where to go instead of Santiago?

Don't worry about it.

In three weeks you're not going to see all the other stuff on your list except at a dead run.

I agree with Ed. Without Santiago, you still have fifteen locations scattered all over Spain. If your three weeks includes your arrival and departure days, you have a total of 19 days to see 15 places. Have you looked at how long it takes to get from one place to another? For example, the high speed train from Barcelona to Madrid takes a little over 2 hours. You must be through security 30 minutes in advance of the train. That means just getting from one city to another takes the better part of half a day, and that is only one location change. All you are going to see is train stations and airports. RS tours (and others) work because they have all of the kinks worked out. You are picked up at the door, taken to the next place without getting lost or having to look for parking or wait for a bus. People on their own simply cannot do the same thing. You don't have two days to fill. You need to cut locations so that you have time to actually see something once you get there.

Read what Nancy posted.. then read it again. You are not on a tour.. the bus is not picking you up at your hotel door each morning and delivering you to the next hotel by dinner time.. you simply have wayyy too much on your plate.

Sit down and work out the timelines.. look up the train timetables or work out the driving times if renting a car. Your trip is unrealistic .
Figure on time for getting to and from train stations.. figure on gas and lunch stops while driving.. and also figure what you want to see in each place. Do you want to see sights or simply drive by them?

Thanks everyone for your recommendations. I will rethink our trip.

September is a great time to visit.
Consider the following itinerary:

Four days in barcelona, then train to madrid
Three days in madrid, then train to toledo
Be sure and spend a night in toledo, then train to seville
Three days in seville
From seville you will head towards granada, the objective would be to spend at least three days in granada with one full day dedicated to visiting alhambra.
Between seville and granada there is opportunity to spend a night in ronda or other locales. Plenty of options to examine.
I am deliberately not trying to fill all three weeks of your time, but i ask that you be deliberate is setting an itinerary which will allow you to absorb the culture of spain and create wonderful memories.
Allow yourself to adapt to the pace of life in spain.

Hi,
I too would say, "Slow down". The more you try to see, the less you will. Years ago there was a movie, I think it was called, "If it is Tuesday, It must be Belgium." Or the old joke: "How was your trip? and the response was, "I don't know I don't have the photos back yet."

I have been traveling for 42 years (geez!). The places I remember, is where I stayed a few days. A fe days and you might meet someone who will become a life long friend like my Rob in New Zealand or Sarka in the Czech Republic. If I plan to visit Santiago de Compostela, at a minimum I think, One day to arrive. One day to figure out where and how things work, Two days to enjoy, and then a day to get out of it and into the next. That is four days per location, minimum. My wife wants to do 7 days per location so we don't miss market day. And I am thinking she is right.

wayne iNWI, off to Spain this March

I spend two to three weeks in Spain every year and I typically stay at four or five locations. I often do day trips from major cities like Madrid or Barcelona. This year I will travel from Madrid to Barcelona across northern Spain through Leon, Burgos, Pamplona, and Zaragosa. It will take me 17 days by train. Since I have spent several weeks in Madrid before, I am thinking of a day trip (AVE train) to Valencia. I consider this trip to be covering a whole lot of ground in a shot time. Your itinerary looks impossible ...