Depends on the season: http://www.flickr.com/photos/technomancy/tags/remoteoffice/ Working outdoors in the summer is the best, but Seattle coffee shops are a nice fallback for the cold months.
What laptop do you use? Are you enthusiastic about its outdoor use?
In my experience for basic stuff like writing words or code, a matte screen in the shadow is fine outdoors.
I do use it in the sun occasionally for short periods, but a) I live in Seattle, and b) it actually gets uncomfortably hot if left in the sun for too long since it's black.
Yes, it surprised me the first time I brought my shiny new Compaq outdoors. :)