I'm having a lot of fun exploring Waltham-area lunch spots. Mi Tierra on Moody St is a good-sized storefront with very impressive Guatemalan and Salvadoran food. I hit the jackpot on my first visit with a pupusa plate, two cripy-chewy, pork-stuffed rounds of maizey goodness.
Excellent sides of fried plantains, black bean mash (far tastier than average), and rice. Not quite sure what that sauce for the pupusas was, didn't look like the typical tomato-based version, more like a tamarind sauce but wasn't very sour. Delicious, too filling, a bargain at $8, with very friendly service. I'll be coming back here soon; gotta try the cheese pupusa.