You shouldn't have to worry about the lower part of the intake as it's shielded, at least in part, by the front bar - just don't spray the water up and into it and you won't have any problems - gravity is on your side there. I would just bag as much as you can reach - water isn't going to maliciously invade its way into your intake, it will only get in there if you put it in there. That's also one of the big draw cards of pressure cleaners vs hoses - they are much more 'accurate' (for want of a better word), meaning you can spray around sensitive areas and, as long as you use some common sense and care, you won't get any water where you don't want it - for example, around door sills and boot lids while they're open without flooding your interior.
