San Andres de Pisimbala or simply San Andres is the tiny hamlet where most people stay.
From Popayan : several busses a day make the 5 hour ride to Tierradentro. Some will drop you off at a place called El Cruz from where it's a 2 km walk to San Andres.
From San AgustÃn : you first have to go to Pitalito and then get a bus to La Plata which leaves at 6 a.m. and 10 a.m. From there you can take bus to San Andres at 4 p.m.