You can play it by ear for now, though I think Kacee is right generally. In SFO you can decide gametime whether to use the pass. As noted, don't bother if your time is short. But if you do you can buy the trip pass for the return for sure.

While LAX is nice, 2.5 hours *could* give you time it may not be a lot, depending on various things. Our SYD-LAX-east coast flight was fine through customs/baggage claim, but then security took almost an hour because they were just opening and the morning bank of flights from Australia had just arrived . . . and they seemed to be checking pretty much every back a second time. We ended up with only about 25 minutes in the lounge before our connecting flight (which was about a 2h15 connection IIRC).