What a little gem! And it's free! (And as another poster mentioned, surprisingly nice restrooms).
But the important thing is that they've done a lovely job creating a place that immerses you in recent history. The videos are super, the oral histories are amazing, and they even have VR headsets so you can experience threshing...plus, mostly for kids but we did it to, there's a chance to virtually drive the oxen. Fun stuff! At the end there's a very cool look at how the museum was conceived and created, with gorgeous photos of the folks who participated.
There was one other group when we were there. Oodles of parking. We even caught a glimpse of El Tiede through the calima haze; the views must be astounding when the air is clear.
We had a picnic at one of the tables past the main building to the left.
Note on wayfinding: the GPS in our rental couldn't find it, but it comes up on Google maps. Coming from the south it's way before El Tanque, despite the name. If you get to Erjos you've gone too far. The turnoff *does not* have an arrow; we went right by it. It just says "Ecomuseo, direcciòn Las Rojas". That's where you turn.
Highly recommended!