AC
I've belonged to two, on opposite ends of the spectrum.
A whole in the wall with just the basics that was fine, and cheap, but it was heavily laden with steroid freaks and really short on some basics.
The other was Golds. One of the big differences was that it was air conditioned and that makes a huge difference, especially in the summer. There can be no underestimating this.
Golds was expensive to join, and ruthless with their billing on late charges. They ran the prices up to 900 pesos and that's when I called it a wrap.
I should say I'm referring to the one on Los Locutores (sp?). There is another in the new Malecon project and I'm sure that is really nice.
They have been doing construction on the Locutores one forever. When it rains, it pours down into the gym making it stink and also very dangerous. They have a huge amount of people in the gym to help lift the weights for you. If they just thinned out the gold jersey helpers by half it would be much better. They are literally in the way more often than anything else. If they aren't dancing with clients or talking on their cell phones, they are either staring at themselves in the mirror or clipping their nails - I've seen that on a few occasions and found it borderline appalling.
It's a very social place, the music is deafening and the loudspeaker announcing phone calls for people and other commands is so loud - so as to be able to be heard over the blaring music - it can be earshattering if you're near a loud speaker (a really really loud speaker). So make some portable music with good headphones a priority.
They are building up to the new opening and continue to wedge equipment into some tight spots. You're literally on top of each other, sometimes that can be good though!
That being said, the 6 and 7 pm. aerobics classes on Monday and Tuesdays are a "can't miss", not to participate, but to witness.
All in all, I'd recommend it if you can afford the $7,000 initiation fee (last time I checked anyway) and the 900 a month. They also have parking (validated?) available.