I'm a big fan of knowing the course I'm running if at all possible. Fortunately, the US Half Marathon is right in our backyard! Literally, the start of the race is just over a half a mile from the Marina Green Monkey Bars at the bottom of Fort Mason Hill.
With this in mind, this is where I'd suggest you launch your run on Saturday. If you like, you can park at the Marina Green and jog the half mile (roughly) to the bottom of Fort Mason Hill and get things started. Here's a link to the course map for Saturday's run-
US Half Marathon Race Simulation Course Map
This course covers roughly 6 miles of the actual course. The run starts from the bottom of Fort Mason Hill where Van Ness Avenue ends at the pier. We've run past this pier MANY times en route to the the Embarcadero.
From the bottom of Fort Mason Hill adjacent to the pier, you'll head SOUTH up Van Ness Avenue. That's right. The start of this race is uphill. You will run along the sidewalk on Van Ness until you hit Bay Street.
Take a RIGHT on Bay Street and continue running on the sidewalk/path adjacent to Bay Street. Bay Street eventually runs into Laguna Street. Take a RIGHT on Laguna Street and continue running along the paved path until you reach Marina Boulevard.
Take a RIGHT on Marina Boulevard. The rest of this run should be VERY familiar to you. Simply follow the paved path on the Marina all the way to the Warming Hut. By the time you reach the Warming Hut, you will have logged 3 MILES.
Grab some water, use the restroom, and head BACK towards the start of our run at the pier. Upon returning to the Pier, you will have logged a total of 6 MILES!
If you feel so inclined, you can easily log 4 of the 6 miles at target half marathon pace by segueing into target pace at the Marina Green Monkey Bars on the way out towards the Warming Hut and maintaining this pace until you reach the monkey bars again on your return.