We too will be coming from CA, SFO Bay Area. Lincoln Field, where the game is scheduled for, is part of a huge sports complex that includes venues for the '76ers, Phlyers and Phillies. There is a subway station right there. It is actually the end of the Broad St line. We are looking at staying in the downtown area because I'm thinking that's where many of the pre/post game festivities will be happening. This will be our first Army-Navy game. Choice of hotels are plentiful but I have a preference for Marriotts. Catching the subway from downtown is very easy. The famous Old City Hall is at the north end of Broad St, in downtown, while the sports complex is at the south end. I think they are about 2-3 miles apart. After you fly into PHL you can catch a cab and also a train to downtown. This train is part of the subway system I believe but on a different line than Broad St. The name of the subway/rail system in Philly is SEPTA. They have a website that shows their system and schedules. Hope this helps you get started.
Cheers...