Mark's geography is perfectly correct re: the route by which Greek astrology could have entered India overland. Certainly, there was a great deal of cultural exchange going on in the regions he outlines. Abu Ma'shar, who grew up in the Silk Road community of Blakh, seems to have been fairly well aware of Indian thought.

The Yavana Jataka definitely comes from Ujjain, thus from the "Western Satraps" on Mark's map. Since the Indo-Greeks of that community controlled the shipping ports of Gujarat, there is a possibility that the first text (or texts) came by sea. Some of the more unique images in the Hindu zodiac -- Virgo as a woman in a boat, for instance -- were traced by Pingree to a specific type of iconography, a sailor's zodiac from Alexandria (see intro to YJ).