I wouldn't trust it without a solid lock...

I never trust it! I've lost 2 already because I didn't want the inconvenience/cost of a big heavy u lock but, in hindsight, the other choice is to just have accept that you might lose it AND sit there in the restauraunt peeking out the window every 2 seconds to make sure it's ok.

Bike theives are sneaky, they have probably noticed that there is a group of bicyclists with nice bikes that park at a particular restaurant on a regular schedule.

Not worth the risk, just get a good lock and deal with it. BTW cable locks seem to be what they go for first, from personal experience (the majority of bikes that me and my friends that have lost were locked with good cable locks.)

I now proudly lug around a big fat kryptonite "forget about it" u lock, and I'm headed towards a personal record of how long I've kept my bike.