I REALLY enjoyed my time in Serifos my friend. Time flies when you are having fun, so the 41 hours felt like 3 days... May be heading back to this island for another couple of nights before our trip is over because it was so special.

To answer your question, a lot of people do speak English. I would say about 3/4 or 4/5 people speak some English, sometimes you will come across a local that hardly speaks English at all, but really it is quite easy to communicate with the local population here.