I use 10w-30 in my GT and know a few other celica owners that do the same. 10w-30 produces thicker oil films than 5w-30, a little exrta protection for those of us that get above 4000rpm alot.
I know people that use 10w-40 in engines that say 5w-30.
You might loose a small amount of gas milage and since you live texas extreme cold is not a problem for you. Matter of fact as hot as it is in texas in the summer 10w-40 would work out well for you.
10w-40 is best choice for engines that typically run high oil temperature. Best choice for engines in daily drivers operated in very hot weather on a regular basis.
In sort, 5w-30 = cold weather, 10w-30 = mild weather, 10w-40 = damn its hot
BTW change your oil every 3k on 5 like toyota says