One consideration is that the Surface Pro is Windows 8 and only AutoCAD 2014 is certified to be compatible. Running any previous version may present problems (display, fonts, open file dialog, etc)..
I run 2014 on a Surface Pro 128 and it works well. If you don't plan on detaching the keyboard and using the Surface like a tablet, you are just as well off with a laptop (running Windows 7) for your situation.
Terry,
How did you get it to run on the Surface. I just installed it on a Surface pro 3 and when I try to run it I get "This application was unable to start correctly"
I'm considering purchasing a Surface but only if I can get it to run Inventor for on the road stuff.