I'd buy the either sex tag! It's only a couple hundred more, BUT in the big scheem of your hunting trip, a couple hundred for the chance at "an elk", ANY elk, would be an easy decision for me. What I might suggest, is hunt the first two days with a bull as your goal! Of course, if a easy cow gave me the opportunity, might have to take the shot. BUT, at least you'd have the options.
Getting a bull is not going to be easier than a cow, IMO! If you're in a good area with a high b/c ratio, AND if while on your hunt the weather cooperates and the bulls are really rutting hard, then abull might just be in your sights!