Check out Bikebike bike shop. They organize rides with cruisers in mind. Oh, and http://www.veloplzen.org/ would be good too.
Cruisers, roadies, tourers, MTBs, cargo bikes, ( hey, how else would Sean get the firewood down there? ) Relaxed pace, eclectic group of people, few zany but harmless types, ( Hi Vanessa! ) last one I attended had 54 riders.