Book: collection of periodical writing

Hi Javi,
You first need to find out what rights to your writing you have. If you are on staff at the paper, it's likely you don't own the copyright to your work (but you might). Check what rights you have.
It may make sense to take your columns or in-depth stories and adapt them to a book, rather than trying to publish an anthology. If most of the columns are about the same subject, you'll have better luck pitching a nonfiction book on a particular topic than just a collection of your writing.
As far as pubilshers interested in a topic primarily devoted to Mexico, you are better off focusing on Mexican publishers rather than American ones. If there's not an American focus (or at least a significant US angle somewhere), few publishers here will be interested.
Good luck!

I second what Nomad has said. Being that she is part of the US publishing industry, and I am very much not, then my comments would have to be taken in that context.

Depending on the copyright issue, you might have a chance of publication in the US. Print-wise, you might consider first examining the catalogues of publishers in the following fields:

-politics/economics
-law enforcement
-sociology (and contemporary culture) texts/books (strongly recommended)
-contemporary anthropology texts/books (also strongly recommended)

If there seems to be a 'fit', then you might consider taking the next step. Additionally, you might investigate the possibility of fashioning the contents as suitable for either documentary, video or radio.

You may have already consider these ideas within a domestic (Mexican) context.

If you are able to pursue any of the avenues mentioned above, and all that this implies, you'll need to be prepared. It is a tough road for native English speakers in the NF field. Assuming that you've published in Spanish, there are other issues that you'll have to contend with, as well.That shouldn't stop you. Hope your research proves fruitful.