Lisa...welcome to the forum!
The hubby and I have walked up to the Akrotiri many times and as everyone has said it's a beautiful place and the views are breathtaking up there! It is still possible to do the walk in the evening as long as you take a torch with you (you may also get some light from the moon too) The footpath takes two routes and one of them diverts you inland on the cliff top rather than on the cliff edge. It is perfectly safe-believe me, there is no way I would have attempted it otherwise! It is easier to return through the village but it takes much longer although it's obviously cooler in the evening therefore less tiring.
Was the Gravia bar there when you last visited? Also highly recommended, it's on the way to the Akrotiri and also serves delicious snacks including breakfasts,salads, ice creams,yogurts cakes etc. We've never been disappointed at either venues...hope you manage to visit them too and simply enjoy!
Suzy X