As per advice from a couple of FTers, I plan to take the BART from SFO to Powell Street, and then jump in a cab to the Crowne Plaza Union Square. I'll have one large suitcase and a hand luggage bag. Fingers crossed all will be OK.
Just one thing... the cab ride from Powell St to the hotel on Sutter Street is only about 5 blocks and less than a mile. Can a taxi driver refuse to take me because the journey is so short?