We'll be traveling in May. I usually just carry zip-off hiking pants and, maybe, a pair of khakis. But, I am wondering if Greek men, or adult male tourists, wear blue denim jeans with any frequency?
Yes, Greek men wear jeans. Especially fashion jeans.
How about women?
YEs, the whole world wears jeans ... unless it's too hot ... so you'd better look at monthly averages, and also deal with global warming (excuse me, climate change)... I've been to greece 13x since '99, 12 of them starting in mid-may or late may. Usually last 2 weeks of may, it's about 65-70 in am, high of about 80-82 around 3 pm, then by 7pm goes down to 70. Perfect, right? But in 1990s, late may had flash heat waves -- lasting 2+ days, up in 90s 12- 5 pm... in the islands Saw people in jeans looking cooked, happy to be in my loose, breezy synthetic & my light cotton capri's. Best idea, 2 days before leaving, get a 10-day weather forecast.
In Europe, I think Greece is where I saw the most people wearing jeans (and also denim jackets)
Jeans are my standard pants anywhere in Greece.
You'll see many locals in jeans so not a problem.