About 40 mi east of his destination, the pilot called Ontario Approach for flight following through the Ontario ARSA. He was asked if he had the current weather for his destination, to which he answered no. He was advised that it was VFR with 3 mi visibility in haze. The pilot requested the ceiling in the L.A. Basin, and was advised that La Verne was measured 2,300 overcast. Twice during radio exchanges with controllers, the pilot gave altitudes which were off by 1,000 ft or more. He attempted twice to descend through a hole in the overcast without success. He then advised controllers that he would reverse course back to Banning. Shortly thereafter he reversed his course back toward La Verne. About 6 min later radar contact was lost in the mountains northeast of his destination. About 20 sec before contact was lost the pilot radioed 'Its getting pretty thick up here.' The wreckage was located at 3100 ft MSL. Toxicological results were positive for methamphetamine (0.50 mg/L blood), amphetamine, and diphenhydramine.