That’s Paula Crist on the left. Crist toured as Zira in a Planet of the Apes show in the early ’70s and later became a stuntwoman, appearing in Battle of the Planet of the Apes and Logan’s Run, among others. She’s also closely associated with early Star Trek and sci-fi fandom, impressing Gene Roddenberry so much that he gave her a spot as a crew member in Star Trek: The Motion Picture. The event above is a convention called the American Quincentennial Celebration held at Grossmont College in San Diego County. See more at Flickr.
UPDATE (9/22/15): The young man on the right is William “Bill” Blake, who played Cornelius in “Meet Zira & Cornelius,” the “promotional roadshow,” as he calls it, mentioned above. Blake is a makeup artist (mentored by John Chambers, who won an Oscar for his makeup work on the original Planet of the Apes film), actor, and special effects technician. More background on Blake and his career can be found here.
Crist and Blake are actually doing professional promotion for Logan’s Run and thus “cosplay” is not exactly an accurate description. The title of this post has been revised accordingly.
2 Warps to Neptune 
https://m.facebook.com/BillBlakeSPFX/posts/899563886796505?ref=m_notif¬if_t=like
The post and post title have been revised.
Due diligence and proper credit is due on this picture. On the right is William F. “Bill” Blake. He also appeared in Logan’s run and he has a large number of other professional credits.
It should be noted, this really isn’t a precursor to what is known today as cosplay. This was live (professional) promotion, by professional people, promoting the film at the time. A better story – which fits into your stated goal – would be about the way films were promoted in those days before the internet.
I have seen all of Bill’s rants and will update the post when I have some time. Had he communicated to me in a professional manner, instead of name-calling, he might have got a better result and we might have learned something valuable about the era and these kinds of promotions, which I’ve talked about before.
Hmmm, I just happened to look this up because I got nostalgic and remembered an article in Marvel’s Planet of the Apes Magazine about two “cos-players” that were doing these incredible PotA recreations. I don’t necessarily remember anything about these being professional promotions even though these were obviously profession quality recreations.