If you stay in the city itself, I recommend sticking very close to the bars, clubs, and restaurants around the central plaza. Esmeraldas has a reputation of being somewhat unsafe after dark. Single women should take particular caution. Bar Asia, on Avenida Bolívar near the main plaza, is a good option. If you're feeling lucky, you can always head to the casino at the Aparthotel Esmeraldas.
The best nightlife to be had in the vicinity is on the beach in Las Palmas. Your best bet is to simply walk the Malecón here and stop into a few of the many open-air beachfront bars. However, be careful, because this area can also get dodgy at night. Stick to well-worn and well-lit areas, and don't go wandering on the beach at night.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.