Dance on the beach
It is a merengue festival after all. If you're inexperienced, stay to the edges of dance areas to give the more experienced performers their space.
The city is the scene
Break away from the malecon to tour the Zona Colonial. This 12-block area is the launching point for Spanish Colonialism into the rest of the Western Hemisphere; Columbus himself walked the streets here. (Hotels in the Zona will also feature merenque bands, so you can dance inside, too.)
Drink some Mamajuana
Originally traced to the indigenous Taino Indians, the modern version of the of the supposed aphrodisiac is a distillation of rum, red wine, and honey mixed with "medicinal" tree bark and herbs. It's recommended to get you in the mood to merengue.
Try some Dominican beer
Given the heat, this is a great way to cool off and the most popular and best is Presidente.
For some alternative music, try "Cuban son"
There are many local clubs that specialize in this kind of dancehall music but the best is probably Mauna Loa at Heroes de Luperon on the Malecon.
Aeropuerto Internacional Las Américas (SDQ)
Travelers arrive here, 13km east of Santo Domingo. Be prepared for intense hawkers offering you everything from transportation to guides to women (if you say no to the offer of a woman, they may counter-offer a boy.) Keep on moving through the crowd to get a licensed taxi, and negotiate your fare before getting in.