Extremadura - How much time?

Edited: It partly depends on how you’re getting around. To me, one full day in each Mérida, Cáceres, Plasencia, and Trujillo, and perhaps a half day each for Zafra and Guadalupe. If you were driving then there are other places off the beaten path, such as, Béjar, Mogarraz, El Barco de Ávila, Granadilla, Monasterio de San Jerónimo de Yuste, Talavera de la Reina, Alcántara, Castillo de Nogales, and Jerez de los Caballeros. You could use the larger cities as bases to visit the other places. I could easily spend a couple weeks in that region.

Thank you for the information. We are looking at renting an auto when we leave Sevilla and working are way through Extremadura and returning the auto in Madrid. From what I have found it appears that public transportation would be quite slow.

I'd like the idea of two days (or the better part of two days) in Caceres.

We are staying in the region for 2 weeks; same apartment the entire time so we can cook, do laundry, have a home base. We want downtime and the freedom to do whatever comes our way but also have some potential plans, such as WOMAD in Caceres and the cheese festival in Trujillo. Area seems to have good hiking and towns of various sizes to explore. We may also do a day trip to Salamanca and one just over the border into Portugal. We'll have a rental as well; it seems best for the area. We've seen a lot of Spain but never this region, which is why we chose it!

The Extremadura region is a really fascinating and historic corner of Spain that is very much under the international tourist radar. In addition to the as mentioned Merida and Cáceres, I'd recommend these sites, (north to south):

Monasterio de San Yuste - the idyllically monastery (still active) that Holy Roman Emperor Carlos V retired to after he was done being the most powerful man in the world ;-)

Parque Nacional de Monfragüe - biosphere reserve, includes stunning cliffs and rock formation, plus many kinds of wildlife (especially noted for its Griffon vultures). Has some really great hiking trials including government-built hides for bird-watching.

Trujillo - This town is where some of Spain’s most famous(infamous) conquistadors came from. The town has a few baroque and Renaissance palaces and an interesting Museum of Francisco Pizarro, who led the expedition that conquered the Inca Empire.

Guadalupe - Has the beautiful Real Monasterio de Guadalupe. You can tour this monastery and its collection of art, jewels, illuminated manuscripts. You can also see two cloisters, one late-14th-century Mudéjar, the other Gothic.

Badajoz - Capital of the Moorish kingdom, the Taifa of Badajoz. It has a nice Moorish historic quarter. The town is dominated by the Alcazaba, a 9th century fortified Moorish citadel.

Zafra - A white-washed walled town nicknamed "Little Sevilla", feels very Moorish. They filmed some scenes from the T.V. show Game of Thrones at the nearby Castillo de Feria, an Moorish hilltop fort.

Jerez de los Caballeros - A very picturesque small town. The old town is surrounded by a Moorish wall with six gates. After it was conquered from the Moors, the town was transferred to the Knights Templar.

Monesterio - unassuming little town that is the heart of the Jamon Iberico production in Spain and is the best at it, home of the real Museo del Jamon.

I'd say 10 nights min to see the region and the sites I've mentioned. Hope this gives a few ideas :)

Great information, I have some homework to do. Thank you for the list of sites