Kefalonia, Kos or Lesvos?

[cowprintavenger]

My friend and I are planning a week's holiday in Greece next May/early June, but we're having trouble deciding between Lesvos, Kefalonia or Kos so I'm hoping some people on here might be able to offer some advice. Our nightmare is the sort of place that's full of drunk Brits, tacky souvenir shops and people hassling you to go into their restaurants so we've ruled out some of the resorts as it's obvious they're not what we want, but for others it's not easy to tell from brochures/guidebooks etc. We'd really appreciate any advice about the islands/resorts below to help us choose.

What we want:
* a smaller resort that's laid back and not too busy
* sandy beach
* plenty of things to see and do within easy reach on foot/by bus
* public transport links so we can explore more of the island and possibly do day trips to other islands nearby
Our main criteria is that we'll be able to get around on foot or by bus

Possible resorts:
KOS - Tingaki, Lambi, Psalidi, Kefalos
KEFALONIA - Katelios, Lakithra, Lourdas
LESVOS - Petra, Anaxos, Molyvos

Thank you!