The Ball is located at the San Mateo Masonic Lodge, 100 N. Ellsworth Ave, San Mateo, CA 94401, just off US 101, north of California Hwy 92 (and the San Mateo Bridge). The facility has restrooms (whew!), a kitchen with refrigeration, small changing areas upstairs and downstairs, as well as some very nice surroundings. Oh yes, there's a dance floor, too!
A fabulous Thai Feast Buffet Dinner will be served at the Masonic Lodge during the interval between the workshop and the ball, but if you prefer to dine at a local restaurant, you may find Yahoo's suggestions for dining in the local area helpful.
From points South: Take US 101 north to the 3rd Avenue exit, going west into San Mateo. Follow 3rd Avenue across the railroad track and turn right on Ellsworth Avenue. The Masonic Lodge is located on the northeast corner of Ellsworth and Tilton. Do NOT park in the Congregational Church parking lot on Catalpa Avenue between Ellsworth and San Mateo.
From points North: Take 101 South to the Poplar Avenue exit. Take Poplar West to Ellsworth, which is the first street after driving under the railroad bridge (NOT a route for trucks because of this low bridge). Turn left (south) onto Ellsworth and go to Tilton.
using this Google interactive area map.