The way I would go to Walmart coming down the Libramiento is make a left turn on to the Carretera. Go east and make the first right turn down. Go a short distance down and turn right. You are now heading west. Drive straight ahead up the hill and go straight and make a left turn into Walmart.
However, I agree with Ferret, only people arriving from the west are allowed to shop at Walmart. Guess where I live.