I don't think those Valley districts are going to break they way they think unless Trump is on the ballot, and even when Trump is on the ballot and wins (like he did in Laredo for example) the incumbent Dem still does pretty well. They gerrymandered the 15th like hell (adding votes from Wilson and Jim Wells counties) and could only flip the district due to Brandon's unpopularity. I think it was a hold in 2024 because of Trump but it's exactly the kind of race that, in a 2018-style blue wave, a supercandidate (like Beto was in 2018) could help a downballot challenger defeat an incumbent republican.
All democrats who tried to act tough on the border FAFO'd
https://www.texastribune.org/2024/08/23/michelle-vallejo-monica-de-la-cruz-south-texas-congress-border/
Whoever they try to run in TX-15 assuming this new map holds cannot be weak.
I have no idea how popular De La Cruz is down there but she doesn't strike me as particularly charismatic or skilled. Not that I trust the Texas Dems not to fuck this up, but all of those valley districts are winnable.