There is a pretty good BBQ place beside the place where you go on the Underground Tour. You can view it on Google Maps:
107 1st Ave S, Seattle
(Right beside the India restaurant, called Longhorn Outpost BBQ) It's a combination of Cajun, sweet spices, etc. Not sure what to call it, but it's for if you want some good eatin's and don't want to go to a fancy restaurant. Two cute girls behind the counter there too. (If they are still there.)