From Archview you can ride some of the trails to the north up around Willow springs boondocking area and a little more north to Dalton wells. This is ok riding and not the wild rock climbing stuff from what I have been on. There may be more if you get maps and explore.
I dont see why you couldn't jump across the highway and get onto Gemini Bridges road and it runs all the way up to Gemini Bridges and then hits 313 which would be about the end of the trail for you. About mid section on Gemini bridges you will see Goony bird rock and there is a side trail to the south in there that goes back to a small campground in a canyon with beautiful rock formations. You can also get on Rusty Nail to the north and Gold Bar to the south. Gemini bridges is just south of 313 near the parking lot and low buck RV parking spot. You cant see it from the highway but Gemini runs along the side of the the rock wall and cuts in to the west at the opening that you see when heading south towards town. I have driven Gemini with my pickup very slowly.
Kens lake is dry camping south of Spanish valley but only gives you access to Metal Masher. It's a beautiful spot with section A out in the open nearer to the lake and section B which backs up to the hills and has a walk to waterfall. You could ride from the camp up into the hills you will see a sign for Metal masher. The entrance to Metal Masher across the stream which goes to the waterfall. Check out the height of the stream bank before entering and having to return. I did it on a dirt bike while hammering the carp out of it.
I have been to several areas around there in the last 3 years but if I had to tell you to go to one place it would probably be Archview. If your MH is your primary vehicle it limits where you can access trails. You also need an orv sticker and it should be ok to cross the highway. Read Ut rules but I believe Az Ut etc honor out of state ORV stickers for limited stays.
Archview has fuel.
