Here's what Trippy members say about Hotel Rex:
"In the Union Square/FiDi/Moscone Center area, these hotels are decently priced for the end of March, coming in at under $200/night: Courtyard by Marriott on 2nd St Hotel Vertigo San Francisco Parc 55 Wyndham San Francisco - Union Square Hotel Rex Alternatively you can look at staying at an airbnb which should definitely be cheaper, but it won't come with the same amenities as a hotel since you are renting someone's house." See More