If you make your own prints, then you can set everything up for Adobe RGB. If you send them out (lab, one-hour, etc) then make sure that whoever is printing can work in that color space. 99% of all places I've run across are sRGB.

If you print an Adobe RGB file in sRGB, the colors will be slightly different. It's probably not a dramatic change and may give you an acceptable print, but you'll be a lot better off knowing what you're getting by having the file set up as sRGB.

I'll bet that the difference between an uncalibrated and a calibrated monitor is a lot more than this - calibrating is a really important thing to do so you know that what you're seeing on the monitor is accurate.