Marilyn, the experts will be chiming in soon, but my vote is if they will grow just fine in Phoenix, Arizona (lyle627), they should grow just fine in Zapata, Texas.
I am way upstate from there, but I will still be planting for at least two more weeks. We haven't had our first hard freeze yet, and probably won't for some time. That far south, I'd say they can plant pretty much anytime from now through April or May, when it starts getting hot.