In lieu of your county extension office, go to the website of Brammert Seed Co. in Muleshoe, TX. They are very helpful folks and have LOTS of grass seed varieties.
If your proposed grasses are warm season grasses, then probably the appropriate time to sow in your area would be March/April, after your last expected killing frost.
If they are cool season grasses, then sow in Oct/Nov.
Also, pray for rain...and good soil moisture for 2+ weeks after sowing (and, birds have already "gone South"...lol.