The Rogue River Valley has some good rides, and I would say that Ashland is by far the best hub (though there are some good rides from Grants Pass also). The LAB awards "medals" to bicycle friendly communities and Ashland made the Bronze List two years ago.
League of American Bicyclists * Press Releases
It isn't up to Portland or Corvallis standards, but it' the only community in southern Oregon officially recognized as bicycle-friendly. The awards are based to a large degree on commuting amenities and advocacy. The Bear Creek Greenway was to have been one of the West Coast's premier bicycling corridors, but the project has been plagued by constant closures (repair for tree root damage) and funding shortfalls. Perhaps one day it will attain the grandeur originally envisioned for it.
Recreational cyclists are often interested in more than just commuter friendliness, though. The RRV still offers lots of good rides. Highway 99 winds through picturesque country along the I-5 corridor, and lots of quality backroads like Old Stage Rd. to Jacksonville offer loop rides in the 20-80 miles range. CycleOregon held its ride in the RRV just a couple of years ago, so you know the potential is good.
While southern Oregon bills itself as "sunny southern Oregon", winters can be quite gloomy and difficult for those affected by SAD. The coast gets fog in summer, but it is actually sunnier than the RRV in the winter. Cycling is very poor on the coast, though.
All of these communities are quite different in character. I would familiarize myself with the idiosynchrasies of each; you'll find that there's more to quality of life than which town offers the widest smoothest road shoulders . Southern Oregon is often seen as having a pronounced "redneck mentality". The population is generally more elderly and less well educated than in the rest of the state, with Ashland being the conspicuous exception. The cost of living in Ashland is also far higher than elsewhere in the RRV. The further east you go in the RRV, the higher the cost of living, the less the annual rainfall, and the more relief you will experience from the libertarian extremism that typifies much of the State of Jefferson. Part of that involves a strong strain of anti-tax radicalism. As southern Oregon grows and grows it is becoming increasingly insolvent. The average resident consumes more in public services than he generates in public revenue. But resistance to tax increases is so strong that most people would rather see the local public infrastructure collapse than to pay their fair share of taxes. Schools, libraries and other public amenities are severely endangered in the RRV.