Answer: In your mild climate many vines will grow year around, which will help you cover your block wall in a hurry. Whether or not a vine will prevent traffic over the wall remains to be seen. Sometimes it's a deterrent and sometimes it is not. Fast growing vines for your gardening region include Bougainvillea (most have thorns), Distictis, Muehienbeckia (Mattress Vine), Petrea (Queen's Wreath), Tecoma (Cape Honeysuckle) and Rhoicissus (evergreen grape).
Some of the best pedestrian-stopping shrubs include those with thorns such as Berberis (barberry) or Rosa Rugosa (trailing wild rose), or shrubs with hairy or sticky foliage. Oleander causes skin rashes in sensitive individuals and Holly (Ilex) foliage has many prickles along the leaf margins which can scratch bare skin. All of the above shrubs tend to redirect foot traffic.
Hope you find just the right plant for your block wall!
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