Fortunately, many of the newer bike racks in San Diego County are of the preferred "inverted-U" variety. In the absence of a good, rim-friendly rack, I prefer to chain/cable the bike to a tree or signpost. The only problem with this is that the security Gestapo at one of the local shopping malls (Plaza Camino Real, for those familiar with the Carlsbad/Oceanside area) routinely impound bicycles parked in this manner. When I shop there, I usually lean my bike against one end of the bike rack, instead of risking wheel warpage in one of the slots.