Thanks for the reply. Im sure the bike trails are not merely dry hard sand however. I believe they are hilly wooded areas on well ridden dirt paths. I think there are both to be some branches,roots, rocks here and there. I dont know if i will ever do off road riding more than once or twice. This guy who invited me used to do it a lot and says hes going to get back into it and invite me along, and im up to try it. Ive seen youtubes of fire roads in Glendale area, they are mountainous dirt roads.
With my biking right now, often i bike from home in mid city and go to paved bike paths (or just stay on roads), so even if when i do this off road riding, i might want to ride on roads from home.
Also though I dont need any more road/commuter bikes with road tires, it's always nice to have options and variety withthem, which is why i picked up the 2 old Bridgestone mB3 bikes to start with when i saw a great deal on them (someone who had to move out of his house.) So I googled about dual purpose tires and came up with the Schwalbe Marathon Cross tire. Im considering that but i might just take my steel framed hybrid with the 40m road tread chinese tires on my first off road ride and see how it goes. If i think im going to do a lot of off roading im thinking im better off with dedicated off road tires like the Schwalbe mountain bike tires to put on my Mb3 with 26" wheels.