Taco Cabana aired 2012 commercials with its spokesperson wearing a “Mex addict” T-shirt. A “Tex-Mex addict” (or “Mex addict”) is someone who crazes Tex-Mex cuisine.
 
“Tex-Mex food addict” has been cited in print since at least 1992 and “Mex-addict” since at least 2000.

 
25 May 1992, Courier News (Blytheville, AR), “NFL success allows Johnson to relax” (AP), pg. 5, col. 2:
“I hope I don’t gain it all back like Oprah,” said Johnson, who is a Tex-Mex food addict.
(Jimmy Johnson, football coach of the Dallas Cowboys—ed.)
 
Google Books
Crazy Plates:
Low-fat food so good, you’ll swear it’s bad for you!
By Janet Podleski and Greta Podleski
New York, NY: Perigee
2000
Pg. ?:
If you’re a Mex-addict, better spend your pesos on lower-fat fare.
 
Google Books
The Empty Coffin:
A Sam and Vera Sloan Mystery
By Robert L. Wise
Colorado Springs, CO: Thomas Nelson, Inc.
2001
Pg. 4:
Throw in the chili, jalapeños, and spices and the result was a Tex-Mex addict.
 
Music & Musicians Forum
ATC
10-03-2004, 04:21 PM
heh is this where i say ‘nacho, close this’ ????
you do realize that mx is the only reason i m now a tex-mex addict.
   
Hold Fast
Monday, January 02, 2006
A Loooooooong Trip…
(...)
As you can see at the left, our bedroom had its own old-fashioned gas fireplace; the hotel was right across the road from a Taco Bell (I’m a Tex-Mex addict) and, better yet, has its own Lonestar restaurant!
 
flickr
That’s right, I’m a Tex-Mex Addict
By ...sherrY Sherry Gibson
This photo was taken on February 3, 2008 in West Columbia, Texas, US, using a Canon EOS Digital Rebel XT.
   
Seize the Deal
Monday, July 11, 2011
Sol Restaurant - Deal of the Day
(...)
Do you dream en Español? Instead of an umbrella, do you prefer to wear a sombrero when it’s raining? Does television static always remind you of delicious sizzling fajitas? If you experience any of these symptoms, you may be a Tex-Mex addict.