Edit: Based on tessellated's response I may not be understanding the question. By workspace are you referring to the different "desktops" you can reach through the numbered boxes on the upper left (in the default config)?
Yes, it looks like awesome's "desktops" are equivalent to xmonad's "workspaces".
From awesome's home page:
> Real multihead support (XRandR, Xinerama or Zaphod mode) with per screen desktops (tags);
It looks like support is there. I might give it a shot again, but tessellated's comment about the difficulty of configuration isn't encouraging, particularly when I already have a working xmonad configuration with most of what I want.
The main difference being that xmonad makes it easy to move a workspace from one screen to another (useful, if you have a laptop and you're unplugging a monitor), whereas in awesome when you remove an external monitor, you go for 2X workspaces to X workspaces and things are moved around.
Can anyone confirm my understanding of this?