I thought I would post this - a bit late - as it may be useful for those who have not been to Plakias before.
My partner and I stayed in Plakias for the first two weeks of September 2010. We are both mostly veggie, though we occasionally eat fish, and my partner cannot eat egg. Having been to Greece around 20 times between us, we found Plakias to have one of the best selections of Greek food for vegetarians of any resort we have visited.
Mostly this was variations on the usual themes - starters such as fried courgettes or aubergines, mains such as briam, stuffed tomatoes or imam. But more tavernas had a wider selection of these than elsewhere. Also some places had other dishes - Mouses had a nice veggie mousaka. There were some different salads too - Kastro had a rocket salad with several other ingredients.
We ate at the following tavernas (in no particular order); Gorgona, Mouses (cheap but busy), Paligremnos (not such a wide choice but we went for the live music on Thursday evenings), Kastro (on a road a little way up behind the village – great views), Sofia (including once for pizza), Christos, Manouses.
We also lunched at On The Rocks (great vegetarian omelette) and Livicon, and breakfasted at Livicon and Argo.
Plakias was also on the cheap side for Greece - at least compared to Alonissos, Pilion, and Zakynthos, which we have visited in the past two years.