You can pick Athletics 0 right at the start of chargen. The careers of Army, Drifter, Marine, Navy, Prisoner, and Rogue thrust Athletics 0 upon you in basic training if you join those careers as your first career choice - which means if you're drafted and are forced into one of the military Services, you'll have Athletics 0 handed to you free at some point.
Likewise, if your character winds up a Drifter, Prisoner, or Rogue at the start of their careers, you get Athletics 0 for free.
Page 55 of the CRB:-
The Athletics skill may be learned or improved but does not use EDU. Instead, use the appropriate physical characteristics (STR, DEX or END). Any physical characteristic can be used to gain Athletics 0.
I could have sworn that Athletics was an exception to the untrained penalty rule, but I might have been looking at the World of Darkness system. In any case, I recommend getting Athletics 0 right off the bat anyway, whether your character is going to be a sleek superagent type or a celebrity pastry chef.