The wonderful Walnut Creek Marriott has changed its parking setup since last year. Now the lot in the hotel building is served exclusively by valet parking. But you will still get your free parking, whether you're staying at the hotel or not.
When you drive up, go into the hotel lot. A valet will ask if you are checking in. If you'll be staying at the hotel, tell them yes and that you're with FOGccon.
If you're not staying at the hotel, the valet will ask if you are here for an event. Tell them yes, that you're a FOGcon member.
You will get a claim ticket from the valet, but you won't have to pay.
Warning! Walnut Creek is fanatical about tow zones, parking meters, and moving your car every two hours (or whatever the local limit is). Use the valet parking, and you can spend the cost of a parking ticket on something gorgeous from the dealers room.