I've been to Po' Shines many, many times. The food is awesome...like my grandmother and mother (both of whom came to the West Coast during the Dust Bowl migration in the 1930s) used to make. Breakfast is one of the most reasonably-priced in Portland (and it's huge...you will not want to eat the rest of the day). You will generally not have to wait in line for a table or need to make a reservation.
Since Po' Shines is operated by the church next door, it's closed on Sundays and they don't serve alcohol. The service can sometimes be spotty due to the sometimes amateur nature of the staff. Just be patient...
In addition to the usual menu, they offer jambalaya, crawfish & gumbo in the season leading up to Lent. They offer BBQ periodically for special occasions as well. Po' Shines is a friendly spot with great food at reasonable prices that should be on anyone's list.