There is no direct public transport link from Lisbon to Salema.
You would either have to take a train or bus from Lisbon to Lagos and then a local EVA bus to Salema.
You best bet would be by EVA Transportes bus from Lisbon Sete Rios Bus Station to Lagos and a local bus to Salema.
I have posted the current Lisbon to Lagos EVA bus timetable in pdf format on Scribd here:
www.scribd.com/doc/12917712/Lisboa-Lagos-Eva
I have posted the current Lagos to Salema bus timetable in pdf format on Scribd here:
www.scribd.com/doc/12917675/Lagos-Salema
