I would plan to stay in Cáceres for a couple of days, and from then do day tours. Guadalupe is a bit far away, but it is doable if you leave early in the day, and in the way back you could stop at Trujillo. Another good one is Mérida. Roman and arab ruins, and a still-working roman reservoir, the Proserpina reservoir. Another interesting place to visit is Olivenza, portuguese until the beginning of the XIX century, with a few manueline churches.

In Cáceres we have stayed at a small hostel right by the Plaza Mayor. It is called Hostal Iberia. I remember that it was quite cheap. An old house reconverted into a hotel, and with nice propietors. On top of that, you can park easily in the Plaza Mayor. I´ll look for the proper address.

>From Cáceres I would cross into Portugal via Valencia de Alcántara, and visit the fortified portuguese town of Marvao. Amazing castle and amazing views.

We did this trip a couple of years ago. We had intended to stay in Estremoz or Vilaviçosa, but we continued driving until Evora (another great place, but the only place in Portugal where we didn´t find good food. Sorry). We drove down almost to the Algarve, but in Monchique we took a turn towards Cabo Sao Vicente, and from then we drove up along the portuguese coast finishing in Santiago de Compostela.

I have a half-written travelogue (the original is in Spanish), so I´ll try to finish it and post it.

Good luck,

Covadonga in Bilbao (Spain)