Around a dozen taxis service San Agustín. They can take you around town and, more importantly, to your lodging outside of town. The rates are fixed but confirm what you'll pay before you get in.
A bus runs the 2km to the archaeological park every 15 minutes (COP$1500) from the corner of Calle 5 and Carrera 14. Another service runs up the hill past El Tablón and La Chaquira to 'La Y.'
Colectivos ply the nearby country roads passing some of the rural hotels, although they are very infrequent and difficult to rely upon.