If your looking for great Tex-Mex you can go to Mia's Tex-Mex on Lemmon Ave. The Margaritas are good. You can also try Mi Cocina they have many locations. If you go to Mi Cocina try the Mombo Taxi frozen margarita with sangria.
Originally Posted by Satamo
+1 on all that ^^^.
Mia's is an institution (lots of Dallas Cowboys memorabilia there -- the place has the distinction of being both the favorite restaurant of Coach Tom Landry and his wife, Alicia, AND of being the place where Jerry Jones and Jimmy Johnson met on the night Jones hired Johnson as the new coach).
As for Mi Cocina, it was founded by the son of the owners of Mia's. But the two are not alike. Not at all.
As for things to do, yeah, The Sixth Floor Museum is a must-see for anybody even remotely interested in the Kennedy Assassination. Superb exhibit, with the sniper's nest completely recreated. It'll give you chills.
Head over to the west side of the metroplex and take a tour of Cowboys (now AT&T) Stadium. Doesn't cost much, and the tour is pretty cool, especially if it's your first time in the building. Bring your camera.
Then keep coming west and spend the day in the Fort Worth Stockyards and the evening in Sundance Square (downtown). It's one of the better "downtown" experiences you'll find anywhere, and it's light years better than Dallas' downtown experience. Tons of restaurants, a piano bar, western themed bars, comedy clubs, etc. Eat at Reata, if you can.
http://www.reata.net/ I highly recommend the rooftop if the weather is cooperative. Fort Worth also has 3 world class art museum located about 5 minutes west of downtown: The Kimbell (a traditional, non-themed art museum located in unique building that is pretty much a work of art itself), The Amon Carter Museum of Western Art (the collections are what you would expect to find given the name -- lot of Remingtons and Russells there), and the Modern Art Museum (the name says it all). Finally, check and see what's going on at Bass Hall (also downtown right by Sundance Square). It's a world class concert hall built with an art deco motif. You won't find anything like it outside of NYC or maybe Chicago. Great acoustics and just a beautiful venue. If you're real lucky, a big name "modern" artist may be playing there. If not, an evening at the symphony can be enjoyable, and the local theater groups regularly put on plays there.
Enjoy your stay!