Lots of good recommendations here. I’m a fan of Pete’s Tako House, Garcia’s, Regio Cafe, El Milagrito, Taco Haven but I prefer Taqueria Chápala on McCulloch. La Fogata (near the north I-10 & 410 area) has great margaritas and enchiladas.
Biga and Battalion are my favorite places downtown.
At The Pearl: Il Sogno has great Italian; La Gloria has an interesting variety of Mexican dishes and good margaritas; The Granary has decent BBQ but relatively small portions. Down on Grayson is probably a good place if you have kids (outdoor seating with space). Grayze (on Grayson St. a few blocks east of The Pearl) is solid.
Additional things: watch the bats come out from under the I-35 bridge at sunset (grab a drink or two from La Gloria, walk down to the Riverwalk and head south, grab a seat at one of the benches after the boatramp, enjoy*).
*Unless the violinist is practicing; we saw about 20 bats compared to the thousands we saw the previous week.