If you are coming out to the Vedder, just hit Freds to pick up the roe since it's right on the river. There is no prime time for fishing, they turn on and off constantly but I have found best time to fish for the Reds has been as soon as the sun gets off the water till you can't see your float anymore. If you are just starting out for salmon, you may not want to start with Red Springs, these fish can get extremely frustrating. I would start out with White Springs in late Septemeber/early October. I would say in order from easiest salmon to catch to hardest would be pinks being easiest, whites after that, chum after that, then coho, sockeye, then Red Springs, and last but not least, the fish of a 1000 casts the Steelhead.
If you get really bored you can always catch some smolts... some of them can get quite big in the Vedder (ones left over from last year that residualized). Best way to catch them and have fun is on a light fly rod (6 wt or less) and a dry fly. Trout rods with worms or shrimp work well too. Those pesky little buggers are always hitting my prawns and roe when fishing for Springs.