I am looking to book a hotel in San Francisco from April 28 to May 3. I am primarily using Priceline, but will follow any suggestions. Budget is to try to stay within $100, but location is more important, so a central location such as Union Square is the most preferable. I am looking for a decent hotel, so I don't know if that means 2 stars or 3 stars or better. Any suggestions on how to research and/or bid would be appreciated.