Laminate them so that the passes can be put in wallets. Get an answering machine to take messages. Call the information line of some of the coffeehouses listed on the WUMB web site and see how they have their information lines. Send out a PR release to the radio stations and local papers about 3 weeks before each event. Consider advertising only for special shows.
Advertising is expensive.
Also send the flyers to all the PR contacts. A good kitchen crew is mandatory. Open the kitchen before the show and at the intermission. Someone to take and sell tickets at the door is required. It would be good to have some sort of banner or sign out front telling people that there is a coffeehouse performance tonight.