David has come up with an excellent itinerary to include all the places you listed. It is very fast-paced, which is fine if that's your style. It has the advantage of having all the 1 and 2-nighters in the first week and less hectic second week. Still, for many of us, it would be too fast. Keep in mind that a 2-hour train ride takes a lot longer than 2 hours. You have to pack/unpack, get to/from train stations, and take into account traffic delays and enough time at the train station to find your train, go through security and board. While security is less stringent than at airports, there can be lines. All bags and parcels and coats/jackets have to be scanned. You may need time to get oriented to each new place to find your way around and use the public transport system. All that means in reality you won't have as much time for sightseeing as it looks like on paper.
May 1 is a holiday in much of Europe. Check what's going on in the city you plan to be in on that day. Train schedules may be affected and trains may be more crowded than usual. Also there are lots of spring festivals, especially in Andalucia. Feria in Sevilla and Jerez, Patios in Cordoba. RS has a list here but you'll have to check for exact dates. Visiting a town during a festival can be a very special experience, but it does mean high prices and many more tourists.
If you don't have air tickets yet, best to fly open-jaw into Madrid and out of Barcelona, or vice versa.
If you aren't staying overnight in Ronda, it's a long journey for just a few hours there. The best plan is to rent a car from Sevilla and drive through the hills, stopping in Arcos, overnight in Ronda, then possibly stopping in Antequera on the way to Granada and dropping the car there. If you can't stay overnight in Ronda, save it for your next visit.
2 nights is enough for most people to see the highlights of Granada.
Toledo is better as an overnight because it gets so many daytrippers from Madrid. On the other hand, Cordoba is an easy day trip from Sevilla. I would consider altering David's plan to spend your first night (maybe 2) in Toledo, then train to Sevilla for 4 nights with a day trip to Cordoba. Cordoba is my favorite Spanish city and I think it's particularly charming in the evenings - much more so than Sevilla. Still, how much time you spend there depends on what your interests are and how many other places you plan to visit.
Lastly, if you can't fly open-jaw, I agree with Priscilla, save Barcelona for another trip. BTW, I was underwhelmed by the Roman ruins of Tarragona and it's a hike to the sights from the train station (not difficult but time-consuming).
Almost forgot - read this excellent article about Spanish trains.
