Which term could be used to describe a person who is easy to speak to?

The term "affable" is used to describe a person who is easy to talk to and approachable. It conveys a sense of friendliness and warmth, suggesting that the individual is sociable and engages easily in conversation. An affable person tends to make others feel comfortable, fostering open and enjoyable dialogue.

In contrast, the other terms do not carry the same connotation. "Aghast" describes someone who is filled with shock or horror, indicating a negative emotional state rather than an ease of communication. "Alleged" refers to something claimed but not proven, often used in legal contexts, which does not relate to a person's manner of interaction. "Ambivalent" signifies having mixed feelings or contradictory ideas about something, which can impede open conversation rather than facilitate it. Thus, "affable" is clearly the most fitting choice for someone who is easy to speak to.