The evening I was scheduled for my class I "Googled" the studio and found it was within a reasonable walking distance (note - reasonable can be five miles for me). I headed out the door of the hotel and then did a sudden unexplained about-face to the concierge desk to check on my walking estimate - just to be sure. Maybe God stopped me - I think so. When I told the concierge where I was going he said I could get there easily in 30 minutes but he didn't recommend it. I would be walking through the "tenderloin" area of town and it wasn't safe. He recommended the underground train. Coming from a small town and not really being a frequent train and bus rider, I hesitated at first. He assured me it was easy and gave me simple and complete directions. "You can't miss it" he said. "Haven't we all heard that before?", I thought. He recommended I take a taxi cab home unless I met someone in the class to walk back to the train station with. I found everything to be exactly as he described and ended up in the right place - though I did have a bit of a walk after I exited the train - and some of it was in the "wrong" direction in more ways than one (oops - wrong way on the street - oops - I think I hit the edge of the tenderloin area!). The energy in the yoga studio and the class was incredible and uplifting. I did meet someone to walk back to the train station with. We are still communicating and I know I will connect with her next year when I return to San Francisco.
Don't be afraid of the train - i.e. something new or unfamiliar. You might just find an incredible yoga class and make a new friend.