People whine way too much about the FAL's gas adjustment.
Seriously, it's not that big of a hassle. I've kept mine on "5" ever since I got it. I've played around with it, and it's not hard to figure out.
What do you mean, I might have to turn a dial? This is too complicated.
Returning to the original question:
Avoid:
Anything with an aluminum/alloy upper receiver.
Anything with the words Hesse, Vulcan, or Century associated with it.
Anything that looks like the gunplumber might not know what he is doing (tool marks, anything that looks bent, forced, dremelled or ground).
Things to look favorably upon:
Springfield SAR-48s.
Anything FN.
Anything with the name DSA on it (it's no guarantee its good, but the rifle does have a warranty).
Imbel receivers (again, not an assurance of quality assembly, but the base receiver is good).
I believe AZEX and ARS are good assemblers, also, but I have no experience with them.
The problem with FALs is that no large maker (except DSA) really makes them for sale in the US anymore. This results in a lot of small makers assembling parts from kits or new stock, and this means that the quality will vary from truly outstanding to truly horrid. There's just so much variance it's hard to give a definitive list.
Mike