In general, I wouldn't expect to see high numbers of deer in 66a or 66. The deer density isn't very high and in most places there is a lot of cover for deer to hide in. Even guys that know the area well don't see high numbers of deer in those units.
Last year was a good year for Eastern Idaho general season units. Last year only around 20% of the deer hunters in those units put a tag on a deer. There are some good bucks to be found but a large majority of the bucks in Idaho general season units are too young to grow big antlers.
Most people in eastern Idaho are going to be confused if you say "West of the River in Bonneville county." I would also think you were talking about West of the Snake River that runs from Menan down to Blackfoot. Most of us view 64 and 67 as North of the river (South Fork) and 66, 66A and 69 as South of the river. Maybe you are talking about the Salt River.