Depends on the folks in the general vicinity.

That said, may I add my own support for a beater. I would never venture to park any single one of the MTB's in your signature or profile overnight on any bike rack, let alone for 5 minutes.

Something similar to the following (singlespeeded K-Mart Huffy Tectra Lite w/lots of nicks and scrapes) should suffice:



Add some grease stains over any white portions of the frame to make it look worse.

Fit a medium-sized U-lock through the crankset and thread it around the nearest convenient frame tube or tubes that you can get it over. Bonus points for getting it through the crankset, seattube, and rear wheel. Put a second lock up on the front wheel, affix it to the object of choice with a heavy loop of chain-link and a stainless lock. As John E. said, try to park this monstrosity next to something nicer or far less protected then your machine.

P.S.: Stick ball bearings in allen key recesses with glue. Prevents anyone from trying to loosen your bars for a "prank."

-Kurt