Now would not be a good time to fish the Rio. Its winter and there will be lots of frozen water. Wait for spring, but if you cant, find some open water and attempt to nymph it.
Patterns/Bugs:
Nymphs: Prince nymphs 12-18, Runt Stone Golden 12-16, Pats Rubberlegs 8-12, 20 Incher 10-14, Flashback Pheasant Tail 14-20, Blowtorch Jig 14-16, Hydropsyche Caddis nymph 14-16. Splitback BWO Nymph 18-22, Juans Jedi Master 20, Juju Baetis 18-20.