The bluegills at Pella will pretty much hit anything as long as the action is right...i usually catch them on small wooley buggers with rubber legs (size 10s) or a size 10 bead head prince. those are easy to tie, and they last a long time. on top try a popper with rubber legs, or a hopper. however, those are just my choices, im sure any fly would work.
as far as aurora...ive never fished it, so i could only give you a general idea. in lakes and reservoirs when i want to locate fish i usually start off with a streamer...usually a black tungsten bead wooley bugger, size 8. i fish it at various depths and speeds, and key in on areas with cover and drop offs. work it fairly agressively, make it look like a baitfish. if it is weedy a slow retrieve with a callibaetis pattern (try just a normal size 14 dark hare's ear nymph) usually picks up fish. those two flies are my top producers in still water.
as far as dries...i dont know for sure. bring along your basic midge patterns, and also size 14 and smaller griffiths gnats and also a selection of adams, size 12-18...those should cover most of what you see on the surface this time of year. my advice is to start off with a streamer though....you might catch anything.
anyone else out there have any advice for a guy flyfishing aurora res?