When you K3, P2, K2, P2, ....K3 it sounds like you are making ribbing with a 3 stitch border on each end. You are right since you end with K3 when you turn you will purl those three, then k2, P2. You want all the purl bumps to line up on each side and all the flat knit "vees" to line up as well. This will be the case on each side. It pays to learn to look at a stitch and work what you see. If the next stitch has the bump right under the loop on the needle it is a purl, purl it, if the stitch is flat it is a knit, knit it.