I hope to be visiting Portland Oregon.

In general what are the seasons like there?

Are there particular streets/neighborhoods with a multitude of coffee shops/book stores?
Can we just go from one place to another without a car?
Is downtown the most active area?
Are there many parks to walk in?
Is there an active nightlife involving staying up late and walking around and talking at cafes/coffee houses, not partying.

Our summers generally start on July 5th...thru Sept it is usually very nice. Then it rains off and on, more drizzle than downpours usually. We get the occassional ice storm around January, but everything shuts down for a day or two, and then life goes on as usual.

There are a few areas that visitors seem to really enjoy. The Pearl District and the NW 23rd area are full of restaurants and shopping, so lots of coffeeplaces. Powell's book is the place to hit...largest independent bookstore in the US. Visiting without a car is very easy. The main areas that visitors hit are all very easy to walk to, but if you don't feel like walking, there is a streetcar. Scarlett uses that daily as she lives in the Pearl, so she could give you the details on that. Yes, lots of parks too.

Powells is fantastic. I'm looking forward to our trip up there so I can try the streetcar out.

A general idea of what late October weather would be? What would be the worst case scenario for Oct. weather?

Blues and Folk Clubs?

I have no idea as far as clubs, sorry.

Weather...worst case...windy and rainy and about 45 degrees. More typical...some wind, rain, about 50 degrees.

Seasons:
I hear summer begins on July 5th. We are excited that today might be dry and in the 70s. July-Sept are the best, warm, dry months. Oct-figure it will be rain, be happy if it does not.
I live in the Pearl District, fun, sort of NY Soho in terms of galleries, good places to eat and where many people come on weekends.
http://portlandtribune.com/pearl/
NW 23rd area, reminds my husband of the Village/West Side..shops, restaurants and almost always crowded but Portland is rarely too crowded.
You can get around town by streetcar..
http://portlandstreetcar.org/schedule.php
or walk.
There are many green spaces in Portland, Waterfront Park, Washington Park, Forest Park, The Portland Japanese Gardens...
is there an active nightlife involving staying up late and walking around and talking at cafes/coffee houses
Yes

Since these questions sound like you have not done much research so far, I also suggest www.pova.com

LOL, I just got up..I see I am repeating mms ! sorry!
But she tells me what to do and where to go everyday so it is only natural that I begin to sound like her

Hawthorne between roughly 20th to 50th streets has an array of eats, clothes, movies, the Powells Cookbook and Gardening Store + a regular Powells branch, and other Book and Music Stores.
The area around SE 26th and Clinton is a nice neighborhood too.

LOL Scarlett

bbqboy--I agree about those areas, but the OP said without a car, so that gets a bit far for most people.

The #14 goes right from DT to Hawthorne.http://www.trimet.org/schedules/r014.htm