I adored Mercado Central! So many foods, crafts, and gifts to see. It took me hours to walk around to see everything.
Many of the vendors i found were willing to haggle. If something seems a bit overpriced go with your gut. Also odds are, if a vendor isnt willing to lower the price, there are 10 other vendors selling the same product.
Make sure to go downstairs in the food area! I had delicious tortillas; 3 different meats for 15 quetzals ($2). I also bought some homemade sweet treats.
Everyone was friendly and i felt safe the whole time, and i was alone. I walked outside as well to take pictures of the cathedral.