Sago palms are very tolerant so they really dont mind what soil they have. But I think that in dry climates its probably best to have soil that retains moisture and nutrients better than sand. In wet climates that have cool winters, sago palms can rot if there is a lot of standing water so mixing soil with some sand might be a better idea. Im not sure about the type of soil you have in Texas, but that might be good enough for the sago palms. Maybe you can mix it with some potting soil also. Some fertilizer in the spring will give it better and faster growth and will probably establish it a little quicker too.
Good luck!
-Alex

The best thing to do for a sago (cycas revoluta) is to plant it on a slope with a free-draining soil, such as a cactus mix. I once had a beautiful, big sago in the corner of my yard and, unfortunately, the soil did not drain, and its roots rotted, and the plant died. Learn from my fail! The one that was on more of a slope is still going strong. For that one I used a mixture of perlite, potting soil and sand to plant it.

Here is a link that might be useful: Brad's Tropical Paradise