I have a pattern for a hat to be knit in the round, but I’m knitting it flat. Most of the decreases fall on right-side rows and call for k2tog. However, the very last row (which is just k2tog around) falls on a wrong-side row. I was thinking that I should just p2tog for this row, but I wanted to ask here first to make sure that’s the right course of action. Would anyone suggest a different decrease or should the p2tog work?
I think p2tog should work fine. Try it. If you don’t like the look try something else. 
Yep, a p2tog looks like a K2tog on the knit row, so that’s what you’d use.