In its 30s, Mercado Juarez Cafe is now a middle-age Tex-Mex restaurant.The fortlike, back-road north Arlington location looks timeworn. But at all four Mercados, the enticing warm salsa and sizzling fajitas haven’t changed.“A lot of restaurants never make it that long,” said Don Bowden, Mercado’s founder and former owner, and a local pioneer of the fajitas-and-frozen-margaritas era of Tex-Mex.“Look around. Even Steak & Ale’s gone. But Mercado Juarez still does pretty well.”Tex-Mex came to town almost 100 years ago with family restaurants like El Fenix and El Chico serving combination plates.It changed in the 1970s, when Texas legalized the sale of cocktails, Dallas restaurateur Mariano Martinez invented the frozen margarita machine and Houston restaurateur Ninfa Laurenzo popularized fajitas.Mercado Juarez still rides that wave, serving sizzling fajita platters, steaks and surprises like a towering platter of mesquite-roasted cabrito ($16.49).But Mercado also serves one of the best green chicken enchiladas in Arlington, and its original Jack cheese-and-onion enchiladas in chili or spinach-mushroom-and-Jack enchiladas (all $10.49).It’s all accompanied by Mercado’s signature warm salsa.“That’s probably our most successful product ever,” Bowden said.“Everybody else was serving a chilled salsa. This is a completely different recipe. Warming it brings out the flavor and fragrance.”The north Arlington location is the most hidden Mercado. The other three cafes are on major highways north of downtown Fort Worth, near the Arlington Highlands and near Las Colinas.But the north Arlington location is tucked away north of Interstate 30 at 2222 Miller Road, between Ballpark Way and Texas 360 (off Avenue J).It remains open for lunch Sundays, and Tuesdays through Fridays, but dinner service is now limited to Thursday through Saturday.Mercado is now co-owned by Bowden’s former managers, but he still dines often at the north Fort Worth location, 1651 E. Northside Drive (at Interstate 35W).The other Mercados are at 125 Interstate 20 East in Arlington, and 1901 W. Northwest Highway (Spur 348) in Dallas; mercadojuarez.com.• More Tex-Mex news: Lorena’s Mexican Kitchen, formerly of Springtown, has moved to 9216 Live Oak Lane at Lake County Marina on Eagle Mountain Lake. Mariscos La Marea, popular at three Dallas and Irving locations, is near opening at 601 W. Northside Drive in Fort Worth.• A reminder: Del Frisco’s Double Eagle Steakhouse opens for lunch only in December, beginning this week.Del Frisco’s is open for lunch Wednesdays, Thursdays and Fridays the next three weeks through Dec. 20.The menu includes a $27 three-course steak “business lunch” or burgers and salads for $13-$16; 812 Main St., 817-877-3999, delfriscos.com.