The restaurant at the Porta Hotel Legendario (9a Calle y 3a Avenida Zona 1, tel. 7943-1022, 7 a.m.–9 p.m.) serves international fare including decent breakfasts, steaks, pasta, and salads.
Some of the best light fare in town can be found at 
Eco Moda Spa and Eco-Café (Calle Real 3-48, tel. 7943-2764, ecomoda [at] esquipulas [dot] com [dot] gt, 8 a.m.–9 p.m. Mon.–Sat.), set in a wonderful 250- year-old home. You can enjoy delicious sandwiches, salads, coffee, and pastries in a delightful garden courtyard. Before your meal, you can enjoy a relaxing massage in a quaint adobe parlor or opt for a sauna or hot-water whirlpool bath.
The owners also arrange visits to their working coffee farm, Finca Las Nubes ($17 per person for accommodations), about an hour away via a rugged dirt road into the mountains, where you can sleep in a rustic but comfortable cabin and enjoy rappelling, walks to the nearby Río Frío and mountain biking, or do nothing at all.
Other culinary options closer to the center of town include La Rotonda (11 Calle, opposite Rutas Orientales, tel. 7943-2038, 7 a.m.–10 p.m. daily), where the pleasant circular dining area is arranged under a large awning. The menu includes pizza ($10 for a large pie), pasta, and burgers. Breakfasts ($2–4) are also quite good.
La Hacienda (corner of 2a Avenida and 10a Calle, 8 a.m.–10 p.m.) is your best bet for grilled steaks, chicken, and seafood with prices in the $10–20 range.
The perennial favorite with Guatemalans is Pollo Campero, just off 2a Avenida southwest of the park, where you can get your fried-chicken fix.