I went to Las Margaritas for my birthday dinner this year and it was great authentic mexican food. I am a vegetarian, and they had a specific part of the menu that catered to vegetarians, which really turned me on the place.
I went with my brother-in-law who is from Mexico and this is also his favorite mexican restaurant. Not just for the food, but for the excellent service. The entire wait staff works together, and like Tony said in his review, they are willing to make dishes that aren't on the menu. If you go, you should try the Horchata, this is a mexican rice based drink that compliments any Mexican dish.
I was surprised with a song and dance from the wait staff that was both hilarious and embarrassing in the same. My waitress put a sambrara on my head and sang to me as my face turned as red as a tomato. Anyways, I would recommend everything about the place (just don't let them know that it's your bday)!