Consider just a shift in tactics - your local Fire Dept may already collect expiring extinguishers from the public and generally needs to dispose of them, talk to your CERT organizer about asking the local fire station to have an open session and *invite* the HOA members (and other members of the puplic) to participate. That way its not under the auspices of the HOA and you probably get a similar turnout.

Our CERT class had a session on fire suppression where we used ~20 of these extinguishers to put out the gas / grease fire Martin suggests. It was conducted at the station, in a clear area, under FD supervision - very easy and made an impression on everyone. We had some good extinguishers and some bad ones, ones that misfired from age, we had to learn to step back and continue suppression with another extinguisher. I had never handled a fire extinguisher to put out an actual fire, I went home and duplicated the experience for my wife and kids in the backyard. I look forward to rotating out one of my extinguishers so we can practice some more, but I wager your Fire Dept would be pretty eager to give folks some hands on practice.