Cheap, non-takeout ethnic food in Somerville/Cambridge
Sorry, a bit late on the reply, but some overlooked places worth checking out include Maria Bonita in N Cambridge (get the machaca/stewed beef, skip the mole), Portugalia in East Cambridge (good salt cod/bacalau), Kolbeh of Kebab near Inman sq (homey Persian; get the kashk-e-bademjan/eggplant puree and the kebabs, ask for tahdig/crispy rice from bottom of the pot).
Finally tried Helmand for the first time last night, and it made me and my 3 guests swoon. We don't have overly high expectations for service, as long as it's competent, and our waiter was a bit slow, but pleasant when you had his attention. None of us drink, so we averaged about 20/person, and we all loved our food. Menu's heavy on beef and lamb, but with enough other options for those who shy away from meat-heavy dishes.
Depends on which country's cuisine you're up for and what price range you want. A few possibilities, with price ranges from semi-cheap to mid-range:
Addis Red Sea (Ethiopian, Porter Square)
Cafe Barada (Lebanese, North Cambridge)
Baraka Cafe (Tunisian, Central Square)
Tamarind Bay, Tanjore, Cafe of India (all Indian, all Harvard Square)
Kebab Factory (Indian, between Porter and Inman Squares)
O Cantinho, Sunset Cafe, Cafe Portugal (all Portuguese, all Inman Square)
Atasca (Portuguese, near Kendall Sqaure)
Mulan (Taiwan Chinese, sort of near Kendall Sqaure)
Changsho (Americanized Chinese, near Porter Square)
Mary Chung (Sichuan Chinese, Central Square)
Qingdao Garden (Sichuan Chinese, North Cambridge)
Helmand (Afghan, near Lechmere)
Koreana (Korean, Central Square)
Seoul Food (Korean, Porter Square)
Forest Cafe (Mexican, near Porter Square)
Le's (Vietnamese, Harvard Square)
Spice Thai, 9 Tastes (Thai, Harvard Square)
the various restaurants at Porter Exchange (Japanese, Porter Square)
Elephant Walk (Cambodian, Porter Square) is a little more expensive then these.
That should give you some options.
Qingdao Garden's strength is really more in Shandong cuisine than in Sichuan, though I do love the place dearly. But they definitely do better at real-deal Chinese than Americanized Chinese.
If Atasca is on the list, I'd have to think that Dali would at least be worth considering. Yes, I know it gets lots of knocks on this group but I really do love their tapas, and the place doesn't lack for atmosphere.
I'd also add Sugar & Spice in Porter Square and The Similans in Kendall/Lechmere for Thai.