Without signs or locked gates they're probably ok but don't use the fact that there's no signs as an excuse to go there. Sometimes there may be no signs but it's obvious that they don't want you on the trail by placing boulders or digging trenches in front of access points. And if you're sneaking onto the access road from another access or dirt road there may be no signs there but they have them at the main road access point and you're still at fault for being there regarless of you seeing the signs.