Make sure the spray cans are completely empty by shaking them and spraying on newspapers outside. If nothing comes out, they should be empty enough for classification as nonhazardous waste --- though this depends on your local waste facility's standards.
Contact your local waste facility to find out if you can place empty aerosol cans in your private recycling bin. Otherwise, place them on the curb with tin cans for curbside pickup, as the California Department of Resources Recycling and Recovery recommends.
Take your spray paint cans to a hazardous waste facility if you're worried that they're not empty. Ask if there is a way to recycle the cans, as some places puncture the cans to ensure that they are completely empty, then crush them for easy recycling at their facilities.