I'll say that all hiring is done directly, I've seen just a couple of cases of agencies working for south american carriers, but about 4-5 years ago.
Most if not all carriers expect you to speak fluent spanish, also check licensing and citizenship requirements.
Argentina and Colombia can be difficult, Brazil next to impossible or at least extremely lenghty provided you have ties with a citizen. All others can be done but not easy if not sponsored by a local company.
With your 737NG time i'll say your best bet is COPA, rumour mill says this year they will hire FO's again. Check thoroughly the already existent threads about them, to figure it out QOL, pay, etc...
Last edited by leondelfierro; 29th Jan 2017 at 19:10.
Reason: spell