I recently had my guitar set up with 12 gauge strings, and noticed some buzzing on the E string. Then I realized...I didn't want 12 gauge..I wanted 11! But then, do you think it'll matter if I just put 11 gauge on, without having to have another set up? Going to the smaller gauge probably will rid the buzzing, but not sure if it'll throw of my inotation..
You will definitely need to setup the action and intonation when changing string size. But these are things which are very easy to do yourself, there is no reason to pay somebody else to set up your guitar.
I think going to the lighter gauge will probably increase the fret buzzing..
Why is that?
Light gauge strings flop around more. I put .11s on (no laughing) my nieces' Hello Kitty strat. The super short scale of that guitar made .9s so loose it was unplayable.