From Guarda your only routing to Salamanca will be as follows:
Train:
1 train per day - Sud Express.
Depart: Guarda 20.42
Arrive: Salamanca 0.05
Bus:
There are two buses per day operated by alsa.es:
Depart: Guarda 12.45
Arrive: Salamanca 16.45
Depart: Guarda 23.30
Arrive: Salamanca 03.30 (Next Day)
Note from whichever town you will be in, in the Serra da Estrela, you will have to get a local bus to Guarda.
