According to FlightAware, it has left from B11, B15, and C23 over the past few days:
http://flightaware.com/live/flight/A...115Z/KPHL/KLAX

Definitely check the monitors after you arrive. Even if there's a gate on your boarding pass, it is quite likely the gate will have changed.
Given that your flight will arrive the same as a domestic one, so long as it is on time, you should be fine.

There's a food court in the area between the B and C terminals. And if you'll have lounge access, there's one of those near the B security.