This was discussed a while back. I'll usually keep one of my CC pistols on top in my range bag and simply drop the mag once I walk inside. When I'm finished and ready to leave, I simply pop the mag back in as I'm walking out the door. It's even easier using one of my revolvers and a speed-loader.
I figure I have 2 alternatives:
1. Don't go to the range (not happening).
2. Ignore the signs and keep a loaded pistol in my pocket. (also not happening since I choose to respect the rights of others).
(Insert random tough-guy quote here)
"See my gun?? Aren't you impressed?" - Anonymous sheepdog
Guns - the alternative to running for your life.