April 20, 2018
I live in Tulsa and ride these trails all the time. There are amazing trails with flow, there are very technical trails, and there are trails that are well past my skill level (intentionally or due to erosion/downed trees). Since it is a sandstone "mountain" expect there to be plenty of rocks, stretches strewn with boulders, a few sandy patches, and tons of post oaks. Don't expect the best mountain biking ever, but its worth a ride. I suspect many of the negative reviews are a result of people being unable to find the rides they wanted.
Generally start at the north parking lot (top of the hill). If you don't know the trails and are looking to avoid technical riding, it would be best to go with someone who knows a route that is right for you. I wouldn't discourage anyone from riding without a guide, but expect some minor inconveniences like hike a bike or doubling back to find the ride you wanted. OR - you will almost always find some other riders in the lots or on the trails, most would be happy to have someone tag along. Once you get back in there, you can go a while between seeing other people even if the trail head seems busy (that's a good thing in my book).
While a plan is in the works, most of the trails are not very well marked at this time. You could certainly get turned around, but it would be hard to get too lost given the available land marks (and that the trails are surrounded by roads, a large creek, and a river). If you find yourself in the Tulsa area, go for a ride. If you don't have a bike with you, you can rent one within riding distance of Turkey Mountain.