It's also possible to get to SPDA from Argentina (e.g. Salta, Jujuy) and Bolivia (e.g. Uyuni, Tupiza). The specifics will vary with which bus services are running, if you're on a tour, if you're driving, weather (mostly in Bolivia), road blockades, border control operations, time of year etc.
Might be worth giving some examples of where to get bikes in town and price, and saying if there's anywhere to put a bike once there. I seem to recall there were lots of stairs at the entrance, is that right? It's also an easy walk, just one road from the NW of town, not much shade though!
Also some coordinates would be good so it shows up on maps. Cheers!