Great Lebanese and Middle-Eastern food and great prices at Nicholas Restaurant. Be sure to order the big bread (a monster flat bread--great for dipping in hummus, or scooping up your falafel.) Bring cash, as Nicholas doesn't accept cards. The meat mezza is phenomenal, but "mezza for one" can actually feed two.
It is the golden age of Portland sandwiches: Bunk on the eastside, Kenny & Zukes at the Ace Hotel, Meat Cheese Bread on 14th & SE Stark, Kenny & Zuke's Sandwichworks at 24th & Thurman, Tributes on NW 23rd, and many more.
Alder Street Carts on 9th and Alder Street in Downtown Portland. My favorite is The Whole Bowl, which makes delicious vegetarian rice and bean bowls filled with avocado, salsa, cheese and other delicious things. Check out http://www.foodcartsportland.com/ to check out other carts. Most food is around 5-6 bucks.