Wow I paid under $200 at the very last minute for a nice place the other day right in Union Square.
Villa Florance was like $178. Kuletos is on the ground floor and is wonderful for lunch or dinner or both.
I recently paid about $140/night for 3 nights at the new Intercontinental SF (4.5 stars), via Hotwire. If you're not picky re exact location, Hotwire can get you some steals!
The King George is showing (on its website) $169 for the 10th and 11th and $269 for the 12th. That is an average of about $200/night.
We stay here quite often. Two blocks from Union Square and charming.
I don't think you will do better, as I did some other checking around, but do check the Chancellor. I believe that on Hotelres.com they showed a twin/twin room for $200. Try that.
The Hotel 480, a block from Union Square is a former Crowne Plaza which has been bought by Marriott and is undergoing renovation. We got a room there last weekend for $169.
You just have to keep trying.
Try looking at sidestep.com - it will pull up the cheapest rates for hotels on various travel websites. If you find something that meets your budget, you can book through the travel website or contact the hotel directly. Most hotels will match the rate if you ask. I was able to get a room at the Hotel Monaco (four star) in union square for $150/night using this technique.
That sounds like a really good resource. Thanks. I especially like the idea of booking with the hotel rather than the booking engine. If you book through them do they charge up front with no cancellation like hotwire, etc. do?
Puter, in response to your question:
When I booked through the hotel, I did not have to pay anything up front. I just gave them my credit card to hold it, and regular cancelation policies applied (cancelation with no penalty up to 24 hours before check-in). If you book with one of the external sites, I am guessing you probably pay it all up front. Some of them seem to have some flexibility with canceling/changing and others not so much.