Club Calloway is very near the Seattle Center, almost literally in the shadow of the Space Needle, and is very easy to find. From just about anywhere in the Seattle area:

1. Make your way to the Seattle Center area. You probably have a favorite way to get there already, so use it. If not, get on I-5 and head towards downtown. Take the Mercer St exit. At the first light, turn right, then immediately left onto Valley St. Drive westward, follow the main road, and in about two minutes you'll find yourself within view of the Seattle Center
2. Find parking, preferrably on the Southeast side of the center, the side that borders on Broad St. There's a ton of parking in this area in the form of pay lots and street parking. Find some and use it. There is a fair amount of street parking with parking meters on Taylor Ave. itself, but if you have no loose change just look around some and you can probably find free street parking without too much trouble. I've indicated some of the nearby parking places in the above image, but there are plenty more.
3. Walk to the intersection of Taylor Ave. and John St. Club Calloway is at 131 Taylor, housed in the building on the Southwest corner of Taylor and John, in the building with the big "DV8" sign. You can't miss it.