Seems some say early / some say late in the middle of summer...what do you think about Mid May? Should we go early or late to minimize big crowds?

Early.

A friend and I were there early in the day in May 2008. It was a free entry day too and we had at least an hour or 2 before the crowds really started...


In pretty well every country I've visited in Europe it pays to be early.

In the middle of summer I would say early, be there for opening. It's not just the crowds you will avoid, it's the heat, which is still a bit much late afternoon.

The last time I checked, May was still in the spring, not summer.

Every place we read said to go early to avoid the crowds. But I was there in late May a couple of years ago, and we practically had the whole Acropolis to ourselves late in the afternoon before closing. We have photos in which nobody else is in the frame and it looks like we are at the Parthenon alone. It was divine, and the weather perfect.

But we were probably just lucky. A woman came along and shooed everyone out when it was time to leave, which was a little before the official time listed so if you do go late in the day, be sure to allow plenty of time.

We went at both times. I preferred late day but only because I found the views of the city and water to be more spectacular (I think it was the sun angle). You can't lose either way.

Whoops, just saw the mid May bit, sorry!
I still prefer early myself (I've been up 6 times at various times of year & day). As the weather can still be a bit variable then I would judge it when you are there. If it is hot then it is better to walk UP when it's cooler & be coming down as it heats up. I suppose it depends where the OP comes from & how hot they are used to, but I live in Greece all year & can still find some May days too warm for uphill.
Also bear in mind that there is very little shade once you are at the top. Take water, wear a hat & non-slip shoes.

<<<<You can't lose either way>>>>
Totally agree! Whenever you get there it's worth it!

Yes, do go early to spend as much time as you want and then take a long leisurely walk down and through the agora. Be sure to go to the new Acropolis Museum - spectacular.