> Let us go -- i.e., we haven't gone yet or "we" would say something like,
> "Let's keep on trucking, you and I." The streets are literal in the only
> sense in which the future tense can be literal, naming something that is
> going to be present tense after some interval.

Point taken, but I think there's a sense in which one would typically say
"let's go, then" when already moving, or at least when the movement is

> Does "he" ever start out actually following the streets, or is the whole
> poem a mental exploration of what might or would happen if he would
> follow up on the first line and go. (I'm still assuming that "you" and
> "I" are the same person, muttering to himself.

This is more what I was getting at.  I think that the closing line of the
poem ("Till human voices wake us, and we drown") wraps the whole thing up
and makes it clear that everything in the poem was essentially a
psychological drama; the "we" in that line can only really be Prufrock
himself [himselves] and all that he has conjured up.  Of course, given the
"inability to get out of himself" that you accurately describe, it's
possible that the events of the poem are nonetheless "literal" insomuch as
they can be said to have an objective existence "outside" Prufrock's mind
-- from the reader's perspective, I mean, since for Prufrock everything is
and can only be subjective.  But I think that the "human voices that wake
[Prufrock]" are the interruption of an inner monologue by outer existence
-- the house guests coming up to his room, perhaps.

And I'm still going to harp on about the idea that "what is it?" is indeed
the "overwhelming question" of the poem, asked by "one".  For me,
everything in the poem concerns a conflict between desire to escape the
shackles of a humdrum existenc -- and it's an escape that can only be
achieved by the deliberate action of voicing complaints, of forcing the
issue; not of merely "starting a scene" (a clever pun) but rather of
absolutely doing away with the currently assumed character and creating
another.  And it's not even the fear of such reinvention that holds
Prufrock back (though such a fear can well be understood by any modern,
angsty reader), but the greater fear that if he ever does so he will be
ignored, trivialised; and that it simply "won't have been worth it".