Not exactly the cheapest place to buy your groceries, but one of the more pleasant and interesting options.
Saturdays year round; 8:30am-2pm in Summer, 9am-2pm in Winter.
If you find any factual innaccuracies in this post, please email me via richard at thingstodoinportland dot org so I can fix it for everyone. Thanks in advance!
In the south Park Blocks by PSU between SW Hall & SW Montgomery [Google map].