I live in San Diego, California and my house property is surronded by
open space brush.  I want to protect the property and house from fire.
 I have no swimming pool nor room for a water tank.  About 150 ft from
my property is a fire hydrant.  I am thinking of buying fire hose and
using the hydrant as the water source to pre-soak and fight a
potential fire.

My questions:
1) Is it illegal for me to use the fire hydrant in an emergency in San Diego?
2) If it is illegal, what is the penalty?
3) What specific tools, hose size and hose coupling size should I buy?
4) Where are best sources for purchase of fire hose?

Well i don't think that it is legal. Your best bet is to contact your
local firestation and or your city office as they should have the
knowledge you seek in your specific area. Among the reasons i would
not do this if you are trying to fight your own fire and the real
firemen show up and your house burns to the ground, you possibly would
not recieve anything from your insurence adjusters as they may say
that you prevented them firemen from doing there job. If you are truly
worried about this make sure that you have home owners insurance,
which you should have anyways as you own your own home. Next look into
smoke alarms and fire extenquishers. If for some reason you are
extremely worried about this you may want to think about getting a
few. Next and which is always important is make sure you have a safty
route out of your house. And if you have a upstairs look into getting
some of those ladders that roll out and attach to the windows.