Hi Tim,
You can use the Staff/Transpose Instrument Key and transpose yourself a capo-ed guitar part while still keeping the Concert Pitch (the pitches that you hear) for other musicians who might be playing with you, or so you can practice along with the file while it plays.
The only caveat here is that to practice along with the file in the right key, you'll have to use the Part drop list and choose the "Guitar" part (or whatever Part you use as your capo-ed part) and display only that. The chord names for that part will be the capo-ed ones. If you show the whole score, then the chord names will be the concert pitch names.
Have fun
Sherry