Eastern Europeans are much more likely to migrate to Italy and Spain than to Greece. Romanians especially. One reason is that Romanian is closer to Italian and Spanish than to Greek.
It's true that the language plays a role in deciding where one prefers to go, but there are also the somewhat more prosaic considerations like the economical ones. The state of Greek economy is nothing like that of Italy or Spain. I have a romanian relative that left Greece after seven years (time in which she learned Greek, accommodated herself and everything) and settled for Italy recently. The hardships exist and this move wasn't easy (from an economical point of view, compared to her previous pre-recession Greece settling experience), but with all that it seems that it still does worth it.
It's also a self fueling process, as the current migrant workers help others migrate and find jobs. The more Romanians there are in a country, the easier it is to migrate there.