Impossible to say, since you haven't listed what "everything" devices you are asking about, but the answer is probably "yes." Every pre-n router I have seen is backward compatible with g and b devices (but not necessarily a devices). My Linksys pre-n router connects to my wife's computer at pre-n speeds (about 275 Mbps) because her computer has a pre-n network card. The same router connects to my work Thinkpad at g speeds, and connects to my old HP printer at b speeds.
So, assuming you buy a pre-n router that is compatible with g and b, and assuming your other devices are g and b devices, yes, it should work.