San Diego Safari Park's Butterfly Exhibit is worth planning for - it's only open for 1 month or less out of this year. We went this year for my mother-in-law Helen's 60th Birthday and she described it as "a piece of heaven"
Sensational Butterflies | Natural History Museum 3 April - 14 September 2014 Wander through our tropical butterfly house full of live, free-flying butterflies and moths and experience one of nature's magical life cycles.
31 Digitally Interactive Exhibits - From Digital Butterfly Exhibits to People-Powered Music Exhibits (TOPLIST)
School-age kids will have a blast at the Coastal Discovery Museum, which offers scavenger hunts, costumes, and a butterfly exhibit (free admission; hour-long guided tours, $10 for adults, $5 for children).