Is the train service in Northern Spain adequate or should we rent a car?

I think a car will give you more/easier access to the smaller villages, wineries and casas rurales ( country B+B's ) that are so nice up there.

www.toprural.com

I think you need to elaborate a bit.
From one of your original postings you was thinking about flying to Barcelona; staying 2-3 days and going to Bilbao.
So does this week include just those tow locations? Or does the week exclude them. Staying in or outside of cities makes the answer different. I assume there are 3 of you on this trip.

Our plan so far is to Fly to Barcelona (3nts) fly to Madrid (3nts) Sevilla, Arcos, Ronda, Granada (5 days) & then back to Madrid. From Madrid to Segovia, Salamanca, Santiago, San Sebastian for the rest of 3 weeks. I thought I would use public transportation for the cities and the south, and then rent a car for the north. Also, do you think reservations are needed for hotels? We'll be there from 6/11-7/1.

Do I understand correctly this is 10 days for Segovia, Salamanca, Santiago de Compostela & San Sebastian???

Here is a map of the train lines. As you can see they are not that extensive in the north.

http://www.raileurope.com/europe-travel-guide/spain/map.html

we found it easier to rent a car in Pamplona and drive ourselves around the north coast and rioja, you can also drive up into france.

11 days to see Barcelona; Madrid; (Sevilla, Arcos, Ronda, Granada); back to Madrid.
So how long will you spend in Madrid on your return?
After that you want to spend 10 days seeing Segovia; Salamanca; Santiago; San Sebastian. That is a lot of journey time. The train from Santiago to SS is about 12 plus hours by train.
For me there is too much travelling. Is that ok with you?
With travel plans this tight yes you do need to reserve…everything planes; trains; hotels. If not you could find your plans going up the creak.

Thanks. I was following Rick Steve's recommendations. If this trip is too tight in the north, what areas would you recommend.

First get rid of Rick Steve's and make room for a book that knows Spain such as Cadogan.

http://www.amazon.com/Northern-Spain-6th-Cadogan-Guides/dp/1860113958

I have to agree with Aduchamp1. On my first trip to Spain I'm embarrased to admit I used Rick Steves as a guide for the number of days on my 2 week trip. It was way way way too rushed. I prefer to have time to enjoy a nice siesta, long meals and just wandering around and people watching - versus just scratching the surface and trying to "see" as much as possible.

With a little less than 3 weeks I'd stick with 2 or at the most 3 main regions.

If you're depending on public transportation and traveling during the summer I'd book hotels in advance.

If I'm going in June with my daughter, do I need to reserve hotels. I did reserve in Barcelona and Madrid, but I was hoping for a bit of freedom in my time schedule so that I didn't have to be somewhere at a certain time.

No you do not have to reverse. I prefer to be flexible and not pre-book. But it does not always work out. Sometime you find all the hotels booked up (reasons like conferences local fiestas etc) then all the hotels in your price range can be booked. So you have to spend more money or go down market and do things like share a bath room or sleep in a dorm.

I still have trouble understanding your time schedule, as you have not answered any questions I raised on the 12th May. If you posted the full outline then maybe some of us can suggests better ideas.

I keep changing my plans as I get more information. Now I'm thinking of the following: 3 days Barcelona
3 Days madrid
1/2 Day Cordoba
2-3 days Sevilla
3-4 days car rental for white hills and maybe a day of scuba diving
2 days Granada
2 days around Madrid-Segovia,Toledo
3 days car rental for San Sebastian and Bilbao
1 day Madrid- or small village nearby.
Will this itinerary be better and less rushed? I could spend more time in the north and less time in the south if you think it's better.

Is it possible to fly one leg of your trip into Malaga? I know Delta has flights to/from Malaga during this time frame (not sure about other airlines).

Your timing looks much better. If this isn't a possibility I'd consider a few tweaks (there are all kinds of different ways to arrange though):

*4-5 days Madrid (w/daytrips to Toledo & Segovia)
*Sevilla 3-4 days w/daytrip to Cordoba on way to Sevilla from Madrid (take AVE train)
*2 days Ronda/White Villages - rent car and tour around area
*2 days Granada - get rid of car on arrival in Granada; FLY from Granada to Bilbao.
*3 days San Sebastian - I would add more time here if you have it. Definately visit Bilbao with other potential daytrips to Hondarribia, Getaria, St Jean de Luz
*final night in Madrid

If you could fly a leg of your trip into or out of Malaga that would make it even better. Malaga is a great city to visit but it looks like you have about 2 weeks so I don't know what I'd cut to add more time in Malaga though...

CathyM's itinerary is a bit more humane.