You have put together a pretty tall order for such a shrub! Oleanders are probably your best bet and there are dwarf types that reach only 4-5 feet in height. Other shrubs to consider include elaeagnus (Elaeagnus pungens), and cenizo (Leucophyllum frutescens). While these plants are drought tolerant they will need some supplemental watering the first growing season to help them become well established and develop an extensive root system. Planting in October or November gives them more time to establish some roots before summer arrives.
I also suggest you visit your County Extension Office and request copies of these two pamphlets: B-5015, "Landscape Development for Texas Coastal Areas" and GC-108, "Plants for Texas Coastal Areas". They will be a wealth of information for you.
Thanks for the question and please stop in again soon.
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