Are you lookin for free places? If so go to lake Mckienzy (near silverton) or the Canidain River north of Amarillo.
I'm a member of the Lubbock Trail Riders. We have some private land for club members to ride on. As far as clubs there is also Renegde. They have a lease south of Post, Tx. The West Texas Boondockers also have a lease. Its around Matador, Tx. You would have to join the clubs to get on the land. I would be happy to give you any info you need on the clubs. If you want to see Renegdes lease they are having an enduro on the First of Feb.
The LTR is close to full right now if we are already not. I realy don't know. We usually meet at the Cooper Caboose on the first and third Tuesdays of the month. We have had a few walk-ins, but most join up through knowing somebody in the club. Post up in the LTR forum about joining if you want to. Traffic is pretty slow in there so it might be a while, but most of the guys are pretty friendly. Frosty is the Money guy and can put in touch the membership chairman (Don't think he gets online much).
What kind of bike do you ride and what type of riding do you like to do.
I know a guy in the Boondockers that I can ask next time I see him how to join. You might try e-mailing the guys that are listed on the contacts they should be able to point you to the membership persons. I was going to point you to the places that John listed.