I've been to all of the gyms mentioned above. the best gym, by far...and i mean by far...is Sosua Ocean Village gym--formely known as Gold's Gym. It has wonderful A/C, new equipment, very well maintained equipment, a boxing room, a yoga room, beautiful bathrooms, hot water, soap all the time (don't laugh...i'll explain later), and you get a nice huge towel when you walk in the door.
They also have great parking with security (it's located inside a gated community), a nice restaurant--not cheap, but good; a beautiful pool--two pools to be exact--that you're entitled to use if you are a gym member, and a beautiful view of the ocean.
I've belonged to nearly all of the gyms in Sosua--the last one being Platinum--but i got tired of bringing my own soap, towel, and listening to excruciating loud music and stupid young Dominican kids talking way too loud and sometimes putting on really loud, stupid music. I'm old, i'm fat...i'm sorry, i cannot listen to loud music anymore and watch kids workout and flex.
The gym is not cheap, but yet it is cheap...it's 2,500 pesos a month--that's about US $58. Not bad. In San Francisco i paid much more, IN Norway, i pay way, way more....and i never had a view of the ocean!!
PS. Oh yeah, they're open on Sunday.
PS-2--one complaint: Since i've joined, i've gained weight and gotten fatter. I don't know if that is the gym's fault or my own?
FRank