My understanding is that "Gold Canopy" service includes your name on the board with the spot # of your car, so you can just walk to your car and don't necessarily have to visit the desk. The "canopy" is the sign or structure above the lot with the spot number and your name listed.

Gold Choice is only at certain locations -- it is a short aisle (usually no more than 10 spaces) where if you book ICAR or higher, you can take one of the cars in those spots for free if you prefer (although if it has XM/NeverLost/etc. there might be an additional fee). More information, and a list of participating locations, here: http://www.hertz.com/goldchoice

What did you reserve at SFO? If an ECAR or CCAR, that might be why it doesn't say Gold Choice. But FWIW all Gold Choice locations are also Gold Canopy (I think...).

-J.