Here is what I learned. You can't drive your UTV in the city limits ($300 fine) therefor, you can't park in Silverton and ride to the trails.
There are a couple of options: For a fee, you can park at the Silverton Lakes RV Park. They charged my $25 to park in a camp spot for the day. It might be a bit more $$$ during high season. This is convenient in that they have a store and bathrooms should you need to use them.
The other option is to park along the side of the road. Once you are outside of the city limits, you can park along the side of the road. The only requirement is that you are all of the way off the road.
I used the RV Park, but most people just park their truck and trailer along the side of the road.
JG