There are no buses from Seville to Lagos during week-ends until 1st June, 2008. There are daily local buses from Lagos to Salema.
www.alsa.es have a 15:30 departure from Seville on Sunday, 4th May, 2008. It arrives Faro Bus Station at 16:30.
There is an EVA bus from FARO to LAGOS at 17:25 arriving 19:40.
There is then an EVA LAGOS to SALEMA bus at 20:30 arriving Salema at 21:02.