On my last few trips to Mexico, I met more and more people on the Oaxaca coast who had caught dengue fever. But now that I haven't been for a few years - is it less of a concern now or has it become even more rampant?
The British FCO seems to indicate that Dengue Fever is still a risk in Mexico:
(Scroll down or CTRL-F to find the passage about Dengue Fever)
It seems that it is.
Here's a news report of quite a few confirmed cases and an increase of 35% over that 5 week period in Oct 2013 (in Oaxaca)
However, Oaxaca doesn't seem to be the leader. Yucatan, Veracruz, and Quintana Roo all had more cases of Dengue than Oaxaca.
Another good thing to consider is that there are next to no mosquitos during the dry season (Nov-May), most of the year.
Another good source: http://www.ciedd.oaxaca.gob.mx/info/pdf/dengue.pdf