Some good news re: Delonte West ... he entered a rehab facility late Monday night, Mark Cuban tells us -- and by Tuesday morning, he already started his programs at the facility. Once Mark Cuban located West, the Mavs owner met with Delonte's mom at a nearby hotel and together they convinced him to get treatment, according to Shams Charania. Now, the hard work begins ... and everyone close to West is hoping Delonte can finally get on the road to recovery.