If you have a nasty looking bike and a really good locking system you should be ok. Leave a good chain and lock at the site and carry a secondary lock with you. Use both when you lock up. Try to move the bike around to different spots so it's not always in the same place every day - predictability helps thieves.

Make sure both wheels are locked and have the seat secured with a chain of some sort. I used to melt candle wax into allen bolts on the handlebar/stem areas...good luck!