This post may be relevant to an audience of one–myself–but I’m posting in case it’s helpful to anyone else. I’ve biked to the airport but I don’t go there frequently enough to consistently remember where the access point to the Guadalupe River trail is, so here are my notes.
Google Maps gives a usable route but you need to jump into Streetview to see where the actual access is–just after the trail goes under [road] you loop back to a crosswalk to a small parking lot and then another crosswalk to the terminal-side sidewalk that runs between Terminals A and B.
Here’s a Streetview embed from the crosswalk point:
Here’s a photo mid-crossing (in the tiny parking lot) looking toward 87/Airport Parkway and showing the trail access point. Guadalupe river trail access is across the crosswalk and to the left.