Think "lodging"—yours or another—when considering your dining options in this region. Hotels tend to have the best restaurants, and you're welcome whether or not you're staying there.
The Pacific lowlands bring together a number of dishes from elsewhere in Guatemala, with a few specialties of its own. No surprise that you'll see a hearty caldo de mariscos (seafood stew) on most restaurant menus, as well as sopa de tortuga (turtle soup). Given the fragile state of the Pacific turtle population, we suggest avoiding that second one. On the topic of what to avoid, you might also be on the lookout for chanfaina, the local variation on the Spanish lamb stew that uses many of the animal's body parts. In this region of Guatemala it's more likely prepared with beef, but still with everything tossed in.