My LDS gives free air fills for life of the tank if we buy a new one from them. AL80 at about $120 or 72 just because it's steel and has better buoyancy characteristics(and on hand, of course) and possible tumbling to remove rust?
I would make the choice on the basis of bouyancy characteristics. Given your location and newness to diving, I assume you are diving wet, with thick neoprene. In that situation, many divers prefer a steel tank, to the alternative of adding a lot of lead to their waistline (and, consequently, pulling their legs / feet down in the water, etc). And, presuming the tanks are steel 72s, the tank is pretty popular, and has remained so for many years, among many divers - not a bad endorsement. The key issue is, as already stated - did the owner take care of the tanks? Sounds like the outside loooks good, but what is critical is whether any moisture accumulated inside, that caused pitting to occur. You won't know until you look.
You mention the price of a new AL80, and the possible advantage - free air fills for life of the tank. That's pretty impressive for a lot of reasons, particlarly considering the new price is only $120. Your friend gave you the steel tanks, so you have little to lose by having them hydro'd. Even if they need to be tumbled to remove any flash rust, you should be able to walk away for less than the $120 for a new AL80, although you don't get the free air. Still, not a bad deal at all, even if you replace the valves (I agree with the recommendation, if the valves on the tanks are the older 'J' valves').
Should I dump the air on the tanks and inspect inside before making the decision? Or is that just a bad idea before hydro?
It is not a bad idea. The air has to be dumped anyway for the hydro. The question is, do you know what you are looking for, on the inside of the tanks?
I'm not sure where to take it to get hydro'ed, either, but I guess I can start with that place in Montebello tomorrow.
Virtually any dive shop can arrange for the tank to be hydro'd. Or, you can check with local fire equipment / fire safety businesses - many of them do the hydros for dive shops anyway, and more than a few - at least here in NC - are willing to deal directly with the public.
My wife wants a steel tank more than me, because she had difficulty with shallow water(<5') buoyancy in the pool with the aluminum tank. Me, on the other hand, didn't notice a lot of difference except 6 pound less weight I ended up using.
And, it is actually the placement of the weight that can make a difference. With a steel tank, the weight is generally going to be positioned higher on your body, and you have a better chance of achieving good horizontal trim. Putting more lead on your waist often contributes to a 'foot low' trim in the water, and helps create divers who swim along at a 45 degree angle, leaving a silt storm trail behind them with every kick.
