Depends on your set up, only time I get salt on the outside is after I've had my hands in the tank. I have a biocube 32 without the lid.I can't ignore them. I clean them every day when I wake up. Its part of my morning routine.
As for how to keep it clean. Its your return causing the water to splash?
I've had issues keeping the glass on my tank clean. I'm referring to the outside part. It always gets water stains, salt buildup, and smudges. Does anyone have a solution for this?