I also did Chitzen Itza. My drunk self called it Chicken Pizza; I thought I was stupid until a year later my Archy prof told the whole class that remembering Chicken Pizza would be a good idea for the midterm
We decided on Chitzen Itza because if I'm not mistaken, it has the biggest area of ruins, and also is the official one of the seven man made wonders of the world.
I've heard there are more "activities" to do at the others (Tulem etc.)