Yes it is. I've played there several times. Four courts. Two hard court (one with a grandstand), and two clay(ish)/sand/gravel courts. The grandstand court is lighted for night play. They charge us 400 pesos per hour.
Terramar has courts available to public for 200 pesos per hour; Nanny Estates (Cabarete) has one court which can be reserved ahead of time for 200 pesos per hour.
I think the Seahorse courts now cost 640 pesos per hr ($US 15/hr), so getting a bit pricey. Maybe Ocean Village or Playa Chiquita are better (cheaper) options.