Who are we in John chapter 3?
11Verily, verily, I say unto thee, We speak that we do know, and testify that we have seen; and ye receive not our witness.
There are several 'we's' mentioned in John 3. The first is a polite form of address, although it may also imply that more than Nicodemus agreed Jesus was 'a teacher sent from God'. Joseph of Arimathea was a member of the Sannhedrin and he also was a believer in Jesus.
The second two mentions of the word 'we' are simply a reference to Jesus as being 'one with the Father' (John 10:30) as God. Jesus was not just speaking on His own authority. Jesus said to Philip 'He that has seen me has seen the Father' (John 14:9), and in numerous other places that He was not speaking on His own authority but was saying what the Father told Him to. Thus it would be true to say that Jesus was saying that to hear Him was equivalent to hearing the Father. His words were essentially the Father's words, as opposed to Him merely being a mouthpiece or prophet.
It is also worth noting that in verses 3,5,7,11, and 12 Jesus used the pronoun I. This would further seem to indicate that there was a point being made here by the use of 'we'.
Jesus was not speaking of anything which He had been told about, or had not seen for Himself. Since He was the incarnate word who was 'in the beginning with God', (John 1:1-4) He personally knew about the truths He was trying to communicate to Nicodemus, rather than having been taught them by God.
On another level altogether, if you are trying to apply the story personally, there are a number of possibilities. Obviously the 'we' of Jesus Himself as one with the Father cannot apply to anyone else. If one identifies with Nicodemus as a seeker after truth, or even as a believer in the midst of unbelief, as Nicodemus appears to be, then that 'we' would apply.