Most parking on the streets surrounding Caltech is for two hours only (enforced!), so we recommend you find a day-long spot in any of the campus parking lots.
Caltech has three parking structures. The closest to the workshop location will be parking structure 3 under the football field near the Cahill building (big orange building on California Blvd). Buy a parking permit from the kiosks near the middle of the lot or request one ahead of time. Make sure you park in one of the open spots (without a name in it) - Caltech security patrols and reports violators. The purchased permits are not Carpool passes - so do not park in a Carpool space, even if there are more than two of you in a car.