Getting DIM values over link_to

I am trying to be RESTful. I have users_controller so that I can see the
profile of a user via user/:user_id .

What I want, is to show a select box (drop down) where I see some users.
I will select a user and click ‘Go’ to go to the user profile page,
meaning user/:selected_users_id

but I cannot get the user_id selected in the drop down. I could, I would
write a link_to helper like this:

link_to ‘go!’, :action=>‘show’, :id=>the value selected in the drop down

any idea how can I do that?