The nightime beach action is in Cabarete...starts around 9pm...the real partying starts around 11...goes to 3 am. Cabarete is also fun in the late afternoon when all the kitesurfers and windsurfers are out. Early mornings are good at Playa Encuentro, between Sosua and Cabarete..especially if you're a surfer. Most of the resorts at Playa Dorada have their own beach parties...and there are booze cruise-type daytime excursions to Bacardi/Paradise Island. Sosua beach is great during the day with the most action on Sundays. There are dozens of small, secluded beaches west of Puerto Plata and east of Cabarete...then there's Playa Grande, just past Rio San Juan...great for a chill day trip and eating super fresh beach prepared right there and served to you right in your beach chair...try a pina colada there - they're made with the fresh fruit served in the pineapple and are awesome...and only around 80 pesos...