An oasis in the Tenderloin
A convenient location for the theater district with all the quality and friendly service you'd expect from a Union Square hotel. Once you step inside the Serrano you'll never know you're in the Tenderloin. But still an easy walk to places like the Great American Music Hall (awesome place to see a show btw). And if you'd like to avoid the street shenanigans it's easy to find a cab. < $10 cab fare to Fisherman's Wharf. 
Yes, parking is expensive. But this is San Francisco, parking is expensive everywhere. Either take the train in to the city or know that you're going to have to budget for parking.
Be sure to check-in in time to enjoy their daily wine reception in the lobby from 5-6pm. Great way to start off the evening. 
Overall, I recommend the Serrano and will stay there again.