I never did finish that engineering degree... but, I would assume that the two 6' long sections of 4" PVC embedded in the ground will probably stay put. However, the connection point with the regular pine 2" x 6" and the Sign will most likely fail; causing the Sign to become just another piece of wind borne debris during the next direct Hurricane.
They mentioned placing signs at each crossing of the Timpoochie Trail, aka the multi-use trail. That could be a lot of signs and obstacles blocking views.
This is a TDC project approved many months ago and is separate from the multi-use path wayfinding project that was recently approved. I think you will find these signs are attractive and they will identify communities along 30A. The set backs are to be in line with the Florida Green book per WC.