Lots of brush and lots of roads. There is a motorized vehicle restriction in place. That means you have to keep your 4 wheeler on "established roads capable of carrying 1500# GVW". Simply put, a two-track road without vegatation growing in the tracks that is wide enough for a pickup counts as an "established roads" and there are alot of them in unit 56.
Although I wouldn't consider access to be an issue, there is private ground at the bottom of all the mountain range, which does limit some access to productive areas.
I think I know why there is suddenly such interest in unit 56....but let me tell you there is not big bucks lurking behind every tree. In fact, several people I know who have drawn the late tag in the unit have been very disappointed with the quality of buck. Don't get me wrong, there are big bucks there, I just think its going to be very crowded and there are going to be some disappointed people when they don't find a mature buck in every draw.
They has been fairly heavy pressure there in the last few years and rumors of some poaching of mature bucks also.
I grew up in American Falls and now live in Pocatello. Several of my friends own property in that unit. I am not an expert there, as the last time I hunted it was for elk but I am somewhat familiar with the area. I don't know your fathers health or abilities, but there are lots of roads if you just want to spend some time driving around. There is some fairly rugged country if you get away from the roads but overall, it is tough to get too far from a road.
Good luck
Lance