Greek was the lingua franca of the Eastern Mediterranean world, Galilee was significantly Hellenized, and Hellenized Jews were ubiquitous in early first century Palestine.
To me, it certainly seems in the realm of possibility that Jesus and some of this disciples could speak and write at least some Greek. The Gospels written in simple Koine Greek, so the authors weren't writing in sophisticated literary Greek.
I don't think the article is fair to Ehrman otherwise. Ehrman does not think the Gospels are utterly unreliable. What he thinks is that you have to work at it to mine the historically reliable information embedded in the scripture.
I'm reading a book by Ehrman now, and he believes these are genuine historical facts as supported by the evidence.
1) The Romans executed a Jewish rabbi named Jesus around 30 AD.
2) Many of Jesus' disciples came to believe they saw him after his execution (aka, the disciples were not lying or fabricating myths).
