Coating galvanized cable so it's rust-proof and sun-proof?
If you are too cheap (re: specific price presumably that of the galvanized cable) to do it right, don't expect miracles - being cheap is expensive (every time you have to replace the cheap item, + the cost of each failure.)

Galvanized is already sun-proof, the only way to make it not sun-proof is to coat it with plastic that's damaged by the sun. 

It's also rust-resistant, but CHEAP cable will be minimally coated with zinc and thus the sacrificial protection of the zinc will soon wear through, exposing steel, and rusting. High-quality galvanized cable will have a thicker coating and a higher initial price tag. 

That or a proper grade of stainless (be sure to factor in the salt exposure for "near ocean" in picking an alloy) will be less costly in the long run than cheap galvanized cable, assuming the rest of the system involving the cable will survive a hurricane. If not, you might just as well use cheap cable and replace it when you replace/rebuild everything after a hurricane.