If you want to visit Cocoar Valley, it is advisable to go with a guide which you can get in touch with in "La Playa retén forestal" (La Playa forest reserve). You can, however, get public transport from Salento's main square to Cocora, specifically to this forest reserve.
Travel tips
If you want to rent a "finca", before you commit yourself, do find out thouroughly what it includes, its inventory, and all services included. Demand clarity. It's not a matter of trust, but of clarity. Sometimes this type of processes are taken in a very informal way which is later to be regretted due to lack of clarity and even comitment from the renters' part. Also make sure its National Toutist Registration is updated. This will support the renting in case you need to make a complaint.