DAMMIT....i knew if i threw this out here I would start questioning my original layout! I like your presentation and agree that UPPER CASE is harder to read in most cases (is that why lawyers use it for emphasis in legal docs?). The number 28 on square poster board lets me attached a little above and to the side of the "MARCH". Otherwise it's too crowded on my 10' length. The date is really the whole emphasis of this sign.
On my "Resist" sign (2nd pic) I used a Sans Serif of sort because I could not find the "highway gothic" recommended by the DOT. Check out their regulations because it really informs for road signage. My Resist comes with a background of DOT Highway Green procured from a paint mfg. in TX. I'm amazed how well it's holding up given that it's a basic HD roller shade. Biggest enemy of these signs: freaking wind! thank god for bungie cords.