I'd rather do the fixed gear/brake stunt. Nothing like a bad experience to convince troublemakers to move their operation somewhere else.

Get some cheap department-store MTB, peel the original labels off, and put Trek decals on it. Do a cheap fixie job on the rear, set the front brakes too tight (with Kool-Stops, preferably). There you go - one suicide machine, to go.

Oh, and put stickers on the handlebars "F*** YOU BIKE THIEVES." If nothing else, it will give them the idea of stealing it.

-Kurt