It's been verified that there was an older and smaller hospital there before the one built in the early '40s. It's also been verified that at least one medical officer was stationed at Coco Solo.
But in calling McCain's mother a liar, you are trending on dangerous ground. She might hear of it, and come beat the snot out of you. :) She is still alive you know, and as of about a year ago, quite hale and hearty. She appeared on the platform with her son on election night.
But, it really doesn't matter, because John S. McCain II was serving the country in the Navy at the time. He could have been born in that Panamanian hospital, and he'd still be a natural born citizen of the US. That "exception" for military (and diplomats) existed before the Constitution was ratified.
re the coco-solo vs colon birth question, the fact that pretty much every adult able to remember what was standard in the canal zone in the 30s is dead or not posting online. This one (what WAS standard for births in cs in the 30s, amador hospital or cs facility?) really is lost in the mists of time. If the question has no political trigger points with people, i would think posting on some of the canal zone-related message boards might turn up an answer, but given the obvious political association, I would be skeptical of some responses now too. that is the only place I would think an answer on what was normal in that time period would be found though.