(Another) Response to Becky's Post, "A Radical Construction of People"

Although I already responded to Becky's post about Constructing people, I have been thinking about it more and I want to respond again. Becky said in her post that you couldn't really know a person until you experience them yourself; you can't trust other people's judgements and opinions. According to the radical constructivist, you cannot know anything outside of your own experience. However, what if you trust another person's judgement enough to take their word as fact (or almost fact)? If a radical constructivist knows somebody who always seems to interpret the world the same way you do, can he or she rely on that person for the "truth" (or their version of the truth that tends to match up with his/hers)? Can a radical constructivist rely on other people for information?