If you're going to take care of yourself, you need to join a gym. If you do a lot of traveling, you shoud join a gym with locations in the places you travel to most often (or one with reciprocal privileges). And if you're going to be fabulous, you should probably do both of the above at Equinox.
I love, love, love the Greenwich Avenue branch of Equinox, in the village. But the San Francisco branch is pretty cool too. It's in a former 1930's bank building, and the men's locker room is in the vault. They left the vault door on for good measure. I think they planned it that way without realizing the irony.