Landscaping a School Sign

The high school where I work just built a new sign at the entrance from the main road.  Within days of being built, it was vandalized.  So last week my principal asked me if I could suggest some landscaping for around the sign that might discourage hooligans from getting up close to the sign and defacing it.

Of course, I had already been landscaping the sign in my mind since the beginning of the school year, but now with the principal’s specific parameters, I am ready to offer a real plan.  Any ideas, readers? 

It is full sun (sign faces east/west), crap soil, no irrigation.  The plants have to be fairly low so that the sign stays readable.  I like the idea of some natives.  I am specifically struggling with how to shape the bed, and with what to stick between the sign and the sidewalk.  Here’s a picture:

Readers who suggest something that actually gets planted will receive a jar of my special homemade Black Walnut Chutney.  Not really, but seriously I will be grateful for your suggestions!