Welcome and be proud you are giving the customer your best by educating yourself.
I’ll usually go over decals and other items that are waterproof and adhered well. If something is taped or suction cupped and can [I][B]easily[/B][/I] be taken off, I’ll do that. Otherwise I’ll handwipe around decals that are peeling, or paper items where the corners are taped diagonally or anything that takes of time.
Good time to discuss training customers who must tape signs, posters, etc.
Have them use Scotch Magic-type (low adhesive) tape and create pull tabs on either the top or bottom of the item by folding over the tape onto itself, leaving enough to still stick to the glass. Makes removal and replacement very quick.
This is exactly what I tell the customer I’m doing. “Training them” I usually let them know I don’t have a problem pulling material off the window as long as it’s taped correctly. (pull tabs, or just taped on the top so you can lift the paper from the bottom pulling it gently off the glass) When I go back in and there’s tape on all four corners and not tabbed, I’ll give them the glare, (they almost always say, "he put it on the window while I wasn’t looking) then I’ll quickly take it off and remove the bottom pieces.