Thanks to the Yelp community, I found Isla, an nice oasis in the madness of Las Vegas. I would come again for sure, if I ever visit come to the Strip again in my entire life.  Guac and chips were fresh and lovely.  Entrees so good.  And I broke my one-margarita rule and ordered a second one.  Service was a little slow but very friendly.  Might have had something to do with the large bachelorette party in the same section.  I do recommend it.  Above average Mexican food! (And I know my Mexican food!)