To take a traffic sign off a sign post, do I not hold the back of the
screw with one pliers while I twist the nut with another pliers?

There's a ONE WAY sign laying on a sidewalk near my house (the result
of a hurricane). I tried to take it off the post it's on by twisting
the nut and it didn't come off. I scratched it with my pliers, so now
I don't want it anymore. So therefore I cased my neighborhood tonight
for another sign for me and I thus found a STOP sign right above a
mailbox. There's no streetlight and so I won't stick out like a sore
thumb standing there on top of the mailbox. I used to write graffiti
so I know how to listen for cop cars with my back to traffic. How long
should it take my to remove the stop sign? Will it have just two
screws like the ONE WAY sign does?