Check engine light

Hi guys, I own a '97 sentra GA16DE and I recently got the check engine light on. After that, I figure that it burns gas like if I'm a rich person. I do not want to take it to the service because it costs me around $30, and appointing that I am in Mexico is a lot of money. I will go to the states next week so I was thinking about getting a scanner for that shit. So my question is. Where can I have one of those shit, I'm looking for a cheap scanner. Thank you