Platinum Gym in the casino has both free weights and lots machines. 1500 pesos per month.
Sosua Family Gym is at the far end of Pedro Clisante (going towards Cabarete). Machines, free weights, very reasonable as well, daily rates, monthly etc
I spent an hour a day in this gym back in 2014. All of the equipment functioned properly,
place was clean and staff very friendly. A friend of mine was visiting down here last year
and said the place didn't look like they'd been taking care it so he ended up using the one
upstairs at the Casino.