The Ellis/O'Farrell Street parking garage is reasonable on a Saturday night ($10.00 max after 5:00 PM), relatively safe, and is only about a 6 or 7 minute walk to CH.http://eofgarage.com/html/rates.htm
http://eofgarage.com/html/location.htm
It's only drawback is it closes at 2:00 AM.
On Saturday night, CH closes at 3:00 AM. If you want to stay that late, just repark your car on the street between 1:00 AM and 2:00 AM.
At that time of night, there's usually plenty of free street parking around the club on 6th Street, 5th Street, Stevenson, Mission, Jessie, 7th Street. Just be sure to check for local street cleaning restrictions which usually start around 12:00 AM, 2:00 AM or 4:00 AM.
On Mission Street, the street cleaning restrictions are in effect every night at 2:00 AM.
On 6th Street, it's also every night, but they do not go into effect until 4:00 AM.
On some of the other streets, it's only on Tuesdays and Thursdays at 12:00 AM.
The street cleaning parking violation tickets are written and cars tagged at about 1 minute after the restrictions go into effect and can be very costly, so double check the restrictions if you choose to park on the street after midnight.
There is one pay lot south of Market Street on Mission between 6th and 7th Street that is relatively safe and only about a 6 minute walk from CH (if you walk up 6th Street). It's usually attended before 10:00 PM and unattended after 10:00 PM. On a Saturday night it's a flat rate of $10.00 for 12 hours or less.