Usually the tourist are looking for an ATM for have cash, but their look for the "ATM" letters when in Mexico you have to look one of the next words: "RED" or "CAJERO AUTOMATICO"
A lot of "CAJEROS" have the English option for don't have problems to understand.... Also remmember that is ok if you pay with your credit card in almost all the stores in Monterrey, that way you don't have to pay the comission for cash
As every big city, the tourist trap more comun is about taxi and little informal commerce at the street.
If they notice you are a tourist they will say that is more expensive than the regular price.
Try to ask some different people of taxi drivers before to take a taxi how will cost you and if in the 'mercados' don't accept the first price of the thing you want to buy, try to ask a better price.