Listening to recommendations I picked La Isabela for this. It had at least a road going to the point of the museum on the map. From Santiago it takes around 30 minutes up a steep mountain by car. The first thing you will see is an observatory which requires a hike going up. I doubt anyone goes up here but there was a busload of people having lunch at the cafeteria. This place has nothing to do with the coffee plantations, which I find a great shame because the road continuing on becomes impassable without a 4WD or risk of getting stuck with your crappy Kia. The road to the coffee plantation is another 2km and I drove it for another 1km before giving up on the road, and I'm glad I did. In fact I think I wasn't supposed to drive in here at all and walk all the way from the cafeteria but anyway the last 1km is doable on foot with amazing views of the surrounding lands. There are even some local restaurants which I doubt anyone ever visits. When you reach the marker on the map there is a sign pointing up the the coffee plantation museum including a UNESCO sign.

A few steps higher and you can see the house peeking through the treeline. After arriving you are greeted by a Spanish-speaking museum guide to pay an entrance fee, including paying for taking pictures. There was of course no ticket or whatever but it was maybe $5 in total. I asked if they get tourists up here and he said very few, plus gave a brief history of the plantation while pointing out some photographs. You can visit the workshops and the kitchen plus upstairs for the living quarters. There was a big viper inside of the rooms sleeping but the guide told me not worry... he did give me a gardenia from the lovely gardens and I was happy to be on my way again. They actually have a gardener taking care of the grounds which surprised me even more. I think it's great that a place is taken care off with the funding they get from the state.

Lastly I recommend going to the coffee drying areas for a good picture of the plantation house from the front.