We found Churrasqueria El Arriero by chance when we got a bit lost and turned onto a quiet side street. It looked welcoming from the outside, so we decided to give it a try for dinner and also to celebrate 2 birthdays. The restaurant is large and spacious, nicely designed and decorated. Folk music from Bolivia's Chaco region (near the border with Argentina) was playing in the background. Our waiter Ricardo was very professional and helpful. The grill master, Jesus, recommended the "lomo" - a very tender cut of beef, and it came to our table grilled to absolute perfection. A good and varied salad bar (I particularly liked the toasted quinoa pilaf). We enjoyed a fine Chilean wine and some local draft beer with our meal. At the end of our meal, suddenly the Chaqueno music stopped and "Happy Birthday" came on the loudspeakers: we were brought slices of delicious homemade flan (with candles!) -- it was very kind of the manager to do this for us and we appreciated the gesture.
Bolivian beef has the reputatiation of not being as tender as Argentine beef, but our Bolivian "lomo" was very tender and truly delicious.
We thoroughly enjoyed our meal and look forward to returning again soon. Highly recommended.