Also a lot depend on whether or not they are true country style ribs. True country ribs are cut from the end of the loin (rib section) near where the muscle connects to the butt; and sometime they will cut a little ways into the butt but not too far in. You can get them with or without bone. These you cook like baby backs.
I've been in stores where they are selling "country style rib" which have been cut from the shoulder (butt) only. If they are from that area you will need to cook them longer, more like spare ribs.
For the above two types I use time as a guide, and then use the toothpick test to check for doneness.
And I have seen some stores selling "country style ribs", that are clearly from the center cut of the loin. These are nothing but boneless pork chops, and they will dry out quickly. These I don't buy.