I typically recommend to my customers to remove the gutter guards or not have them installed at all, in exchange for having me come by every other month or so for an inspection. For the cost of having a set of guards installed all the way around the average house here in FL it is close to $500. I usually charge $20-$40 depending on the fullness of the gutters for a cleaning. All this really entails is walking the perimeter of the roof line with a leaf blower, clearing the downspouts from the roof with said blower, and then blowing any debris off of the house or hard surfaces/patios, and into the mulch bed or yard for decomposition during the normal yard work. Most houses take 20 minutes or less.
When the roof is too steep or if there are solar panels that are right to the edge and there is not enough room to safely walk, I do this instead:
I have a 24ft telescoping pressure washing pole with a gutter cleaning hook at the end, with normally has a downward facing single nozzle that I replaced with a T and installed (2) 9gpm 40° tips. My pump runs at full throttle about 10gpm 4200-4500psi. So by using 18gpm it cuts the pressure down to about 1800-2000psi. It is more of a last resort because the set up is longer and I usually only do this when I am going to be pressure washing the whole house anyway since it does result in quite a mess.
If they are permanently mounted gutter guards, either bolted or screwed into place, it will be hard to convince the owner to remove them. One thing that I run into is that smaller leaves from trees like Crepe Myrtles tend to lodge in the drainage holes, then catch other leaves leading to a build up of leaves that end up covering the guards and forcing the water to either back up or flow over the gutter, thereby defeating the entire purpose of the gutter in the first place. Other guards that are clip-ins or otherwise held in place by only tension, tend to pop out with any pressure washing force is applied to them, or if a heavy enough object lands on them (fat squirrels) they drop into the gutter creating a hole for leaves to fall into leading to the clog they were supposed to prevent.