The problem that you'll have right now is that MANY of the best places are either shut down or are carryout only because of COVID.
First, barbecue. With all due respect, Lockhart is overrated and not worth the trip. The best bbq in San Antonio is at 2M (leaves everything in Lockhart in the dust, reliably):
https://www.2msmokehouse.com. Second place, with much shorter lines is South BBQ, which is curbside and patio only right now:
https://www.southbbqkitchen.com
Tex-Mex: there are tons of choices. Depending where you are in the city, there are lots of good options. In the downtown/southtown area, I send out-of-towners to Rosario's. Everyone likes their margaritas. Very popular. Just down St. Mary's street from there (across from the school) is a hole in the wall called Cascabel which is awesome for lunch. I know Rosarios is open, but I don't know about Cascabel.
Pollos Asados:
https://www.bestpollosasados.com. There will be lines. COVID status unknown. A good second place is Al Carbon Pollos Asados
https://www.facebook.com/ALCARBONPOLLOSASADOS
Burgers: Respect for Chris Madrids, a long-time San Antonio tradition but they've had a change of ownership. I haven't been there since, but they might still be good. The original family opened another place, if that's the style you want: Diana's Burgers on Zarzamora:
https://www.facebook.com/Dianas-Burgers-1861218407306877/
Better Burgers: Mr. Juicy -- opened about a year ago by Andrew Weismann, a very respected high-end local chef. They are simply the best burgers in town. Fight me. He has two locations now. Both are just North of downtown. The fries are simply phenomenal as well. I promise you. Go for the fries.
Serious hat-tip to Hornetguy. Great stuff on his list. A few comments: Hot Joy and its sister restaurant Barbaro are carryout only, again because of COVID. Bakery Lorraine (one is at the Pearl) is simply the best patisserie and has the best viennoseire in all of Texas, and maybe this side of the Atlantic. Again, fight me. Cured (also at the Pearl) has received multiple James Beard nominations and is quite good.
Just reopening yesterday is a great fine-dining option: Maverick.
https://mavericktexas.com First class service, great wine list and cocktails (assuming they hired the same bartenders). In the same neighborhood, about 0.5 mile away is Bliss. Same category: impress your date sort of place.
For Pizza: Dough (Northside and downtown) or Playland (downtown) COVID status unknown. I can also recommend the Sicilian-style at Barbaro on McCullough. Barbaro is a great cocktail place, but carryout only. The arugula salad, chicken parm and meatballs are very good too.
Chinese noodle soup: Kung Fu Noodle. Terrible name. Authentic Sichuan noodle place on Bandera Road (northwest side).
Best wine bar in SA, but only takeaway (COVID): Little Death on N. St. Mary's St. They also sell great cheese and have fresh bread every day. Just put yourself in their hands. The place looks like an old gas station overrun with graffiti (right next to Burger Boy, which is not bad either, drive through only - again COVID).
South Alamode Panini and Gelato. Terrible name. Great Gelato, made by an Italian woman and her American husband; they met in Italy. The Panini are really good too - I go with the Havenese or the Sottobosco. To go only - COVID. Get a pint of gelato and your troubles will vanish. Unless you've been in Italy recently, you haven't had better gelato.
https://www.southalamode.com
Dang! I almost forgot Pinch Boil House. Viet/Cajun seafood boils, curry bowls, Bahnmi when their baker is working. Really, really good. Downtown:
https://pinchboilhouse.com My pick for dine in is the Pinch fries, but they get steamed and lose their crunch to go. The boils are very good to go, however.
That should get you started. DM me what kind of food you want, and I'll know where it is. Just sorry you're coming during COVID. There are lots of great places doing carry out only.