This is the link to a decent article on downtown Cancun. It's fairly accurate, but I will point out that JC Penney hasn't been in Plaza Las Americas in years, Home Depot has moved to a new (huge!) location, and El Parque de Las Palapas does not mean "palm tree park". Also, Calle Tulipanes has more than "a couple" of cafes. It's MAINLY cafes! Some good ones too. Oh, and, if you ask for directions, many times you will find that people will just give you an answer so they don't seem stupid for not knowing where a place is located....but they probably have no idea where you are tryiing to get to. So, even though the author of the article seemed quite confident that people were eager to give him CORRECT directions, don't fall for it.
http://www.chron.com/disp/story.mpl/travel/5654740.html