Food Stalls in Portland's Saturday Market
I do not recommend eating at Portland's Saturday Market (at the Burnside Bridge).
I have personally witnessed some disgusting food prep. techniques here - dirty pans being reused and such. Other than elephant ears, beer and hot dogs, you'll do your stomach a favor to skip your lunch here.
I think Portland Farmer's Market (at PSU) is a far better choice.
This is only held on Saturday mornings until 2PM.