Was just there the other day trails are in great shape, it's dry and loose out right now great condition to ride quads
If you are not that experience in the dirt I would stick to green trails or blue trails. The black diamonds are usually singletrack with some rocky sections sometimes. There's a lot of elevation changes at Metcalf. Like trail one will imediately go up and then down. There are some long downhill sections also. Also there are 3 main trails in the park 1, 2, and 3. The distance of each trail goes up with the number. You can also link the trails in some places. In my opinion 2 is the easiest/flattest sorta.
When you go in drive up or in your case ride up to the office. Have you ticket ready, like on your phone. The signal is spotty up there but they have wifi so you can just whip out the email on your phone. They will have you also sign a bunch of waiver stuff on your phone and they will issue you a liability waiver card so you don't have to keep signing the waiver everytime you come in. Then they'll tell you where you can park, they have green X's marked in the parking lot where you can park. But I guess you can park just about anywhere if you are riding in.
Then ride. If it's your first time there ask for a trail map. There is a trail map near the restrooms also. It is possible to ride all the trails at metcalf in one day also. Also they have a new motocross track if that's your thing and it's MUCh different than it used to be lots of elevation changes. It was dry and marbley when I rode it. Also want to point out a lot of the trails are whooped out, like in a lot the black diamond singetracks you will go around a corner and there will a series of little whoops, if you let off the throttle it'll suck.
They also have air. So if you are going to air down before hitting the dirt you can air back up when you hit the pavement. I think it's across from the restroom there is even a tire changing station there also.