I usually use HotelTonight when I travel to San Francisco. Full disclosure, up until recently I had a friend in the North Bay that I usually stayed with for a few days, so the need to find something wasn't quite as present since if I had to, I could stay with her and travel back and forth to the city, so waiting for a last minute deal didn't stress me out. Now, you can use Hotel Tonight further in advance, so I definitely recommend checking out what options they have for your time frame, especially if SF hotel prices make your eyes go wide.
Most recently I've stayed at:
- Le Meridien in the Financial District. I got this one through Hotwire and was very pleased. Very nice hotel, close to the Embarcadero and transportation.
- The Westin near Market St. It's a Westin, they're pretty much all the same.
- The Griffon on The Embarcadero. This was probably my favorite of the hotels I've stayed at. It's NOT a big room, but it is nice, great location (right across from the Ferry Terminal, close to AT&T Park [a big plus for me], Market St. transportation, etc.)
- The Zeppelin in Union Square. This was relatively new at the time and more of a boutique hotel. It's nice, bigger rooms than the Griffon, but is on the edge of Union Square that is closer to the Tenderloin, which is good to keep in mind. Still safe, I walked back there late by myself with no issue, but some don't like nearing that border if it can be avoided.
- The Mystic in Union Square, this one is right by the Stockton/Sutter garage and closer to Chinatown. Nice, but an older property and similar boutique style room. This one has an option for a $14 breakfast per room that is good!
- The Herbert Hotel on Powell. I actually really liked this one and it was a great deal through Hotel Tonight. This one is VERY simple, not a lot of amenities in the room, and not ALL rooms have private baths so it'd be important to check (most do). It was great for me on the trip I stayed in it, as I was a solo traveler and mostly just sleeping there and keeping my stuff. It's super close to Union Square and the cable car. Breakfast is included at a nearby restaurant. Helpful staff. But again, it's almost a higher end boarding house in some ways and doesn't offer much beyond a clean and safe place to sleep.
Feel free to ask any other questions! I love SF and have gone there annually for the past few years.