If you want to work on AC the first thing you should pick up is a
decent manifold guage set. If your AC hasn't been converted you'll want
a guage set with R12 connectors. Most of guage sets I've seen at the
local FLAPS are garbage, but that just may be my neck of the woods.

The guage set will tell you whether you have pressure in your system.
There are other things to check (fuses and wiring) but if you don't
have any freon then the rest of the check up process won't be very
helpful in the short term.

If there is no freon in the system, the next thing is to find out why.
A vacuum pump will be needed to evacuate the system (prior to
charging), If you can't evacuate the system, then there is a leak that
will need to be fixed. If the evacuated system won't stay evacuated for
long (say 24 hours) then you have a leak that should get fixed.

As to driving in desert in the Summer. You can do it. Where loose
clothing (shorts are a good idea) and have a wet rag to douse your self
with (in the dry desert you'll be surprised at how well that cools you
down.) And bring lots of water for drinking.