I used to live in the Valley and hunted all around Rio Grande City, Roma, and Zapata. Found one point on SPI. Now my area is Frio,Dimmit, and LaSalle counties. Good surface hunting here. Welcome aboard.
What can you tell me about Zapata? I have in-laws that live down there I'm wanting to go do some artifact hunting down there.
Been a while since I've been there but it's typical of small border towns. Not much to offer. If you can get in on a place to hunt, the results are good. Lots of agate and petrified wood, plus flint. I've found points made out of all three plus one out of Jasper. Quite a few bird points but, as typical for So.Tx., the unstemmed blades are the most prominent, Matamoros, Kinney, Catan, Abasolo, Refugio, and ET's.
If you can get in on a place to hunt, the results are good.
So far, I have guaranteed access to a few ranches. I guess it's a good thing that my BIL wears a big, shiny badge, carries a big, shiny gun and has big, shiny lights on his truck. Pretty likable guy, unless you're a poacher or an illegal!