If the places we go aren't implicitly marked as illegal its safe for one to assume they are not illegal to ride on.. there are no signs disallowing motorized vehicles.. not our fault if they don't mark it.. hell there arent even discovery pass required signs
While I agree with you, with the way today's environmentalists think, that line of thinking is what causes us to loose legal places to ride.
For example, since the 2005 rule, the USFS says their roads/trails are open only if they are so designated on the Motor Vehicle Use Maps.
(MVUMs). They even admit on their MVUMs that not all their roads/trails are so marked on the ground and that it is the motorized operator's responsibility to ensure they are on a legally open road. I have copies of the Colville NF and the Idaho Panhandle NF MVUMs. They are also available at the BLM Map Room in Spokane Valley as well as online. And they are free!
But it's not all bad. We have just opened an additional 160 miles of roads in the south end of the Colville NF for OHVs. So while a lot of places are open, we are getting additional mileage. And even though the Colville NF has completed their forest-wide travel management planning, the previous forest supervisor has stated (and I see no reason the current forest supervisor won't discontinue it), they are now going to look at small areas within the Colville where additional roads/trails can be opened.
And there is an initiative within the state legislature to open all roads in WA state with a speed limit of 35 MPH or less to OHVs. While that's primarily aimed at ATVs and dirt bikes, we are finally getting this state to be more OHV-friendly - like Oregon and Idaho are already.
As for your statement about Discover Pass (not discovery pass), This is something new and I'm sure not all places where it's required may not have posted signs yet (just about every place I've been where I thought it was required had them posted. I've seen this not only here in eastern WA, but also out near Cle Elum as well as on the west side of the Cascades). Again, according to the law, it is the recreationist who is responsible to display the Discover Pass in those areas where it is required. Information is available online for this as well. It is changing as the law is interpreted.
I would like to encourage you to change your thinking about where you can legally ride. Just because it doesn't say you can't ride there does not mean you can.