I found Belfast city to be relatively quiet after dark. I do remember walking by the SAS and it seemed kind of out of the way but looked to be a very nice hotel from the outside. I would say a 10 minute walk is about right and if you like walking it shouldnt be a problem. I didn't feel unsafe walking out at night but mainly because there really wasnt many people out other than me. I was staying at the Hilton so it may have been the path I was taking back to the hotel. I only used a taxi once and that was from a busy strip of bars and there was plenty of taxi's available. I dont know that you will find a lot of random crabs around for flagging down though.