Fort Point has been running their taproom at The Presidio (39 Moraga Ave) for a while now, but a new flagship release is a legitimate occasion — Park Pale Ale is distinct from their core lineup and designed, by name at least, to be a crushable outdoor beer. Expect the usual taproom food situation, which means snacks and brewery fare rather than a full kitchen.
The Presidio location is not BART-accessible in any practical sense; drive in via Lombard Street and park inside the Presidio itself — lot near the Main Post is your best bet and tends to be free. Don't mess around with street parking on the Marina side and walking in.
If you've got two hours: get there close to doors, order the Park Pale Ale first while they still have the release-day energy going, grab a table outside if the weather's cooperating, and skip the second round somewhere else — the drive out of the Presidio takes longer than you think.