Thanks to its famous market Chichicastenango has become a star attraction du on Guatemala's tourist trail. I highly recommend you arrive the day before. Strolling around the 2,000-odd stalls that the local Mayans set up is far more agreeable early in the morning. By 10am you'll find more tourists in the streets than Amerindians.
I was, however, saddened to see that Chichicastenango had lost much of its authenticity. Once away from the rabble, I settled down on the top steps of Saint Thomas Church. It's one of the oldest in the country and Mayan religious ceremonies are still held. I also recommend you tackle the 30-minute walk to the sacrificial shrine at the top of the hill. Chuchkaujaus, the Mayan high priests, still perform rites at the site.
In short, providing you organise your visit and avoid the hordes of tourists, Chichicastenango is a charming place to visit.