BBQ near Riverwalk in SA?
I'm sorry to say there's very little barbecue in San Antonio that compares to the best of Central Texas. There are quite a few other quality options near the riverwalk, but not cue. Two bros. is the best I've found in SA, but that's definitely not a short cab ride. And also just good, not outstanding.
I haven't found anything in SA that compares to Central TX BBQ but there are a few decent places. Most are far from the Riverwalk - however . .Mr J's on S New Braunfels is just a short, colorful cab ride away.
Mr J's is definitely a dive - and not like a TX BBQ Joint dive . .but a "looks like it's falling down/I can't believe this is a licensed business" type of dive . . so, depending on what you're looking for, it may or may not be for you.