There is metered street parking on the blocks adjacent to Union Street; typically, these are limited to one hour, but some have been updated to allow you to pay electronically, and they are not limited to one hour.
There are two parking garages nearby:
Union Street Garage
1550 Union Street
Between Franklin & VanNess
www.uniongarage.com
Wells Fargo Union Laguna Garage
1910 Union Street
Between Laguna & Buchannan
www.pacificparkonline.com