Routes -
Many states have traffic volume information online. This lets you see which routes have the least traffic. Of course, these are usually only the main roads, not the back roads. The usual term is AADT - Average Annual Daily Traffic - the total number of cars in both directions for that measuring point on the highway. In the Rocky Mountain West, summer numbers are much higher than annual averages. Also, most highways have higher volumes in the morning and evening commutes.
Here's the Kansas state AADT map:
http://www.ksdot.org/burTransPlan/ma...rafficdist.asp
(Kansas also has county road traffic data)
My rule of thumb -
Under 500 - Super sweet
500 to 1000 - Sweet
1000 to 2000 - O.K.
2000 to 4000 - Iffy
4000 to 8000 - Risky
Over 8000 - Insane
Shoulders change everything in terms of safety - still it's not terribly pleasant cycling on an Interstate with 10,000 vehicles even if there is a wide shoulder. (Most Western states permit Interstate riding.) Back roads tend to be more roundabout than state or US highways, so you end up doing more miles, but I think every touring cyclist loves the absolutely empty road ride that can only be found on back roads. Back roads with no shoulders that are used as shortcuts to the mill by 2000 vehicles are no fun at all - far more dangerous than riding on a highway with a shoulder. Very few states have good shoulder information. Shoulders have this nasty tendency of disappearing 10 miles out from town with cars zooming by at 70 mph. Given the unreliability of shoulders, I almost always choose low traffic volume.
Churches - 20 years ago churches were much more open - even unlocked - but in an age of liability and vandalism, they are much less willing to take risks. Also, in little towns, the minister may live 20 or 30 miles away. Just like factories and stores, many churches in small towns are barely hanging on. Catholic churches usually have the priest living next door in the rectory. Other churches vary. Often there is a sign out front giving the minister's name. Ask if so-and-so lives in town, then call him or her. Years ago the minister would often say, "Sure" and come by to open up the kitchen and bathrooms. Today, unfortunately, it is often more complicated - requiring the approval of various committee members etc. So do not take offense if the minister says, "No." or even "I don't know."