When I'm in Las Vegas and craving some good Mexican food, I go to Tacos Mexico.  My brother who lives in Vegas turned me on to this place, and I just visited them this past Friday and Saturday.  On Friday I ordered the Carne Asada burrito with everything in it, and then on Saturday, the El Pastor burrito.  You definitely get your moneys worth.  The burritos are so big, I had to cut in in half.  I had half for breakfast and half for lunch.  Their salsa is also great.  The drive-thru takes a while, but it's worth it.  My boyfriend ordered the Chorizo breakfast plate, and that was also a good sized portion.