Living in Salem, I haven't had any desire to camp near Mt Hood. The
NF campgrounds are pretty busy because it's so close to Portland. Most of the NF campgrounds have sites that are too short for your rig.
Interactive mapMt Hood is beautiful. Timberline Lodge is a must see. The Columbia River Gorge is also a must see.
If I were camping near Mt. Hood, I'd consider boondocking. You should be able to find a good spot for dispersed camping not too far from Government Camp or one of the ski areas. I've done a lot of skiing, hiking, and mountain biking in the area, but no camping.
Maybe you can get some ideas from this old post:
Boondocking near Mt Hood? This is close to Cooper Spur which is a neat area.