Moved to Upland, CA 3 years ago and just bought a 450XC quad and looking for riding buddies. Don't necessarily have to be from Upland. If interested, let me know or if you know of riding clubs close to San Bernadino/Upland, let me know as well.
look into www.so-calatv.com.
it's a atv forum for your area. i live by temecula cal. it's about 45 minutes south of you, me and my friends mostly ride mx. you should check out the mx parks www.milestonemx.com in riverside, www.ridecemx.com in hesperia, and www.racetown395.com in adelanto near hesperia.