You can pick the kind of ground you want to soar over in L.A.: the ocean or the inland mountains and valleys.
If you prefer to see the water slipping past beneath you, head for Dockweiler Beach Training Park (12000 Vista del Mar, Playa del Rey, Wed.–Sun. 11 a.m.–sunset). For a higher-altitude adventure, head to the San Fernando Valley and up to Sylmar Flight Park (daily 10 a.m.–sunset). You can go tandem with an instructor at Sylmar Flight Park (recommended for first-time gliders) or get bold and try a solo ride (which starts at an altitude of five feet out on the beach at Dockweiler).
For a good school and rental facility, call Windsports Soaring Center (818/367-2430, http://windsports.com [1], prices vary). Windsports provides all the equipment and training you need, so all you have to bring are a good pair of athletic shoes, a bottle of water, and, of course, a camera.
Links:
[1] http://windsports.com